<PAGE>   1


                             SECURITIES AND EXCHANGE
                                   COMMISSION

                             Washington, D.C. 20549

                                -----------------

                                    FORM 10-Q

                   Quarterly Report Under Section 13 or 15(d)
                     of the Securities Exchange Act of 1934

                                -----------------


For Quarter Ended March 31, 2000                   Commission File number 1-5341
                  --------------                                          ------


                                ELCOR CORPORATION
             ------------------------------------------------------
             (Exact name of Registrant as specified in its charter)


         DELAWARE                                                     75-1217920
-------------------------------                               ------------------
(State or other jurisdiction of                                 (I.R.S. Employer
incorporation or organization)                               Identification No.)


         14643 DALLAS PARKWAY
SUITE 1000, WELLINGTON CENTRE, DALLAS, TEXAS                          75240-8871
--------------------------------------------                          ----------
(Address of principal executive offices)                              (Zip Code)

Registrant's telephone number, including area code                (972) 851-0500
                                                                  --------------


     Indicate by check mark whether the Registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act of
1934 during the preceding 12 months (or for such shorter period that the
Registrant was required to file such reports), and (2) has been subject to such
filing requirements for the past 90 days. Yes X . No   .
                                             ---    ---
     As of close of business on May 1, 2000, Registrant had outstanding
19,610,514 shares of Common Stock, Par Value $1 per Share.


<PAGE>   2


PART I. FINANCIAL INFORMATION

ITEM 1. Financial Statements

                                ELCOR CORPORATION
                           CONSOLIDATED BALANCE SHEET
                           (Unaudited, $ in thousands)

<TABLE>
<CAPTION>
                                                                       March 31,    June 30,
ASSETS                                                                    2000         1999
                                                                       ---------    ---------
<S>                                                                    <C>          <C>
CURRENT ASSETS
Cash and cash equivalents                                              $   4,852    $   4,186
Trade receivables, less allowance of $963 and $967                        78,647       72,866
Inventories -
         Finished goods                                                   21,295       15,377
         Work-in-process                                                     355          180
         Raw materials                                                    13,337       10,213
                                                                       ---------    ---------
                  Total inventories                                       34,987       25,770
                                                                       ---------    ---------

Prepaid expenses, insurance receivable and other                           2,936        8,352
Deferred income taxes                                                      2,371        2,111
                                                                       ---------    ---------
                  Total current assets                                   123,793      113,285
                                                                       ---------    ---------

PROPERTY, PLANT AND EQUIPMENT, AT COST                                   262,520      212,704
         Less - accumulated depreciation                                 (84,892)     (76,984)
                                                                       ---------    ---------
                  Property, plant and equipment, net                     177,628      135,720
                                                                       ---------    ---------

OTHER ASSETS                                                               2,651        3,177
                                                                       ---------    ---------
                                                                       $ 304,072    $ 252,182
                                                                       =========    =========

LIABILITIES AND SHAREHOLDERS' EQUITY
CURRENT LIABILITIES
Accounts payable                                                       $  25,437    $  18,067
Accrued liabilities                                                       11,717       15,817
                                                                       ---------    ---------
                  Total current liabilities                               37,154       33,884
                                                                       ---------    ---------

LONG-TERM DEBT                                                            88,700       63,000
DEFERRED INCOME TAXES                                                     19,642       18,047

SHAREHOLDERS' EQUITY -
         Common stock, $1 par                                             19,988       19,988
         Paid-in-capital                                                  58,834       59,586
         Retained earnings                                                85,387       64,632
                                                                       ---------    ---------
                                                                         164,209      144,206
         Less - Treasury stock (379,367 and 465,149 shares, at cost)      (5,633)      (6,955)
                                                                       ---------    ---------
                  Total shareholders' equity                             158,576      137,251
                                                                       ---------    ---------
                                                                       $ 304,072    $ 252,182
                                                                       =========    =========
</TABLE>

See accompanying notes to consolidated financial statements.


                                       1
<PAGE>   3


                                ELCOR CORPORATION
                      CONSOLIDATED STATEMENT OF OPERATIONS
                           (Unaudited, $ in thousands
                             except per share data)


<TABLE>
<CAPTION>
                                               Three Months Ended         Nine Months Ended
                                             ----------------------    ----------------------
                                              3-31-00      3-31-99      3-31-00      3-31-99
                                             ---------    ---------    ---------    ---------
<S>                                          <C>          <C>          <C>          <C>
SALES                                        $  90,448    $  70,735    $ 267,973    $ 227,802
                                             ---------    ---------    ---------    ---------

COST AND EXPENSES
       Cost of sales                            70,607       53,132      201,023      169,506
       Selling, general and administrative      10,002        8,898       29,352       28,982
                                             ---------    ---------    ---------    ---------
INCOME FROM OPERATIONS                           9,839        8,705       37,598       29,314
                                             ---------    ---------    ---------    ---------

OTHER INCOME (EXPENSE)
       Gain from involuntary conversion            403           --        1,292           --
       Interest expense, net                      (239)        (464)        (760)      (1,468)
                                             ---------    ---------    ---------    ---------

INCOME BEFORE INCOME TAXES                      10,003        8,241       38,130       27,846
       Provision for income taxes                3,792        3,126       14,439       10,527
                                             ---------    ---------    ---------    ---------
INCOME BEFORE CUMULATIVE EFFECT OF
       CHANGE IN ACCOUNTING PRINCIPLE            6,211        5,115       23,691       17,319

CUMULATIVE EFFECT OF CHANGE IN
       ACCOUNTING PRINCIPLE                         --           --           --       (4,340)
                                             ---------    ---------    ---------    ---------

NET INCOME                                   $   6,211    $   5,115    $  23,691    $  12,979
                                             =========    =========    =========    =========

INCOME PER COMMON SHARE-BASIC:
       Before cumulative effect of
          change in accounting principle     $     .32    $     .26    $    1.21    $     .89
       Cumulative effect of change
         in accounting principle                    --           --           --         (.22)
                                             ---------    ---------    ---------    ---------
NET INCOME PER SHARE-BASIC                   $     .32    $     .26    $    1.21    $     .67
                                             =========    =========    =========    =========

INCOME PER COMMON SHARE-DILUTED:
       Before cumulative effect of change
          in accounting principle            $     .31    $     .26    $    1.18    $     .87
       Cumulative effect of change in
          accounting principle                      --           --           --         (.22)
                                             ---------    ---------    ---------    ---------
NET INCOME PER SHARE-DILUTED                 $     .31    $     .26    $    1.18    $     .65
                                             =========    =========    =========    =========

DIVIDENDS PER COMMON SHARE                   $     .05    $   .0467    $     .15    $     .14
                                             =========    =========    =========    =========
</TABLE>

See accompanying notes to consolidated financial statements.


                                       2
<PAGE>   4


                                ELCOR CORPORATION
                      CONSOLIDATED STATEMENT OF CASH FLOWS
                           (Unaudited, $ in thousands)

<TABLE>
<CAPTION>
                                                                          Nine Months Ended
                                                                              March 31,
                                                                        --------------------
                                                                          2000        1999
                                                                        --------    --------
<S>                                                                     <C>         <C>
CASH FLOWS FROM OPERATING ACTIVITIES

         Net income                                                     $ 23,691    $ 12,979
         Adjustments to reconcile net income
            to net cash provided by operating activities:

                  Depreciation and amortization                            7,930       6,825
                  Deferred income taxes                                    1,335       4,340
                  Gain from involuntary conversion                        (1,292)         --
                  Cumulative effect of change in accounting principle         --       4,340
                  Changes in assets and liabilities:
                     Trade receivables                                    (5,781)     (3,101)
                     Inventories                                          (9,217)     (1,355)
                     Prepaid expenses, insurance receivable and other      4,398      (7,131)
                     Accounts payable and accrued liabilities              3,270       3,157
                                                                        --------    --------

                  Net cash provided by operating activities               24,334      20,054
                                                                        --------    --------

CASH FLOWS FROM INVESTING ACTIVITIES

         Additions to property, plant and equipment                      (49,816)    (22,236)
         Business acquisition, net of cash acquired                           --      (5,298)
         Insurance proceeds from involuntary conversion                    2,310       3,187
         Other                                                               504        (304)
                                                                        --------    --------

                  Net cash used for investing activities                 (47,002)    (24,651)
                                                                        --------    --------

CASH FLOWS FROM FINANCING ACTIVITIES

         Long-term borrowings, net                                        25,700       9,500
         Dividends on common stock                                        (2,936)     (2,729)
         Treasury stock transactions and other, net                          570      (5,970)
                                                                        --------    --------

                  Net cash provided by financing activities               23,334         801
                                                                        --------    --------

NET INCREASE (DECREASE) IN CASH AND CASH EQUIVALENTS                         666      (3,796)

CASH AND CASH EQUIVALENTS AT BEGINNING OF YEAR                             4,186       5,240
                                                                        --------    --------

CASH AND CASH EQUIVALENTS AT END OF PERIOD                              $  4,852    $  1,444
                                                                        ========    ========
</TABLE>


See accompanying notes to consolidated financial statements.


                                       3
<PAGE>   5


                                ELCOR CORPORATION
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                                   (Unaudited)

1.   The attached condensed consolidated financial statements have been prepared
     pursuant to the rules and regulations of the Securities and Exchange
     Commission. As a result, certain information and footnote disclosures
     normally included in financial statements prepared in accordance with
     generally accepted accounting principles have been condensed or omitted.
     The company believes that the disclosures included herein are adequate to
     make the information presented not misleading. These condensed consolidated
     financial statements should be read in conjunction with the consolidated
     financial statements and related notes included in the company's 1999
     Annual Report on Form 10-K. The unaudited financial information contained
     herein has been prepared in conformity with generally accepted accounting
     principles on a consistent basis and does reflect all adjustments which
     are, in the opinion of management, necessary for a fair presentation of the
     results of operations for the three-month and nine-month periods ending
     March 31, 2000 and 1999, but are, however, subject to year-end audit by the
     company's independent auditors. Because of seasonal, weather-related
     conditions in some of the Company's market areas, sales can vary at times,
     and results of any one quarter or other interim reporting period should not
     necessarily be considered as indicative of results for a full fiscal year.

2.   In the first quarter of fiscal 1999, the company adopted Statement of
     Position 98-5, "Reporting on the Costs of Start-Up Activities," issued by
     the Accounting Standards Executive Committee of the American Institute of
     Certified Public Accountants. This Statement of Position requires, among
     other things, companies to expense on a current basis previously
     capitalized start-up costs. Adoption of this Statement of Position resulted
     in a nonrecurring $4,340,000 charge, net of tax, and is reported as a
     cumulative effect of change in accounting principle on the Consolidated
     Statement of Operations for fiscal 1999.

3.   On September 15, 1998, the company experienced an explosion at its nonwoven
     fiberglass roofing mat plant in Ennis, Texas. The explosion significantly
     damaged a drying oven and caused less extensive damage to the remainder of
     the mat manufacturing line. There was no damage to a separate mat line that
     runs in parallel to the damaged line, nor was there any damage to the
     company's Ennis, Texas shingle manufacturing plant. There were no injuries
     from the explosion. The damaged line was restored to partial operation in
     December 1998. By March 1999, the damaged section had been replaced. In
     June 1999, the line was operating at line speeds equivalent to line speeds
     at the time of the explosion.

     The company submitted claims totaling $17,492,000 for property damage and
     business interruption. In February 2000 the company reached final
     settlement with its insurance company. In total, the company received
     insurance proceeds of $17,017,000 on the claim. Assets with net book value
     of $3,990,000 were destroyed in the explosion and were insured for
     replacement value. Overall, the company received replacement value payments
     on the property claim in excess of the net book value of destroyed assets
     in the amount of $1,292,000. This amount was recorded as a gain from
     involuntary conversion.


                                       4
<PAGE>   6


4.   In the fourth quarter of fiscal 1999, management approved a consolidation
     plan for Chromium Corporation's reciprocating engine components business.
     All operations for this business activity at the Lufkin, Texas facility
     have been transferred to the Cleveland, Ohio plant. Costs to relocate
     equipment and other nonrecurring consolidation items of about $2,600,000
     were incurred and recorded to expense in fiscal 2000. The Lufkin, Texas
     facility will be used for Cybershield's products for digital wireless
     cellular phones and other electronic equipment.

5.   In June 1999, the Board of Directors declared a three-for-two stock split
     payable in the form of a stock dividend, which was distributed on August
     11, 1999 to shareholders of record on July 15, 1999. Appropriate references
     to number of shares and to per share information in the consolidated
     financial statements as of March 31, 1999 have been adjusted to reflect the
     stock split on a retroactive basis.

6.   Effective January 5, 2000, the company increased its unsecured revolving
     credit facility from $100,000,000 to $125,000,000 and extended its term to
     December 15, 2004. There were no significant changes to the financial
     covenants or to the interest rate the company pays for either LIBOR based
     borrowings or prime rate based borrowings or to the commitment fee paid for
     the unused portion of the line.

7.   In accordance with the requirements of FASB SFAS No. 131, the company is
     segregated into two segments: Roofing Products and Industrial Products. The
     Roofing Products Group consists of the various operating subsidiaries of
     Elk Corporation of Dallas (collectively Elk). These companies manufacture
     and sell premium laminated fiberglass asphalt residential and accessory
     roofing products, together with nonwoven mats used in manufacturing asphalt
     roofing products and various industrial applications.

     The Industrial Products Group is comprised of three businesses: (1)
     products used in digital wireless cellular phones and other electronic
     equipment; (2) remanufactured large diesel reciprocating engine components
     used in the railroad and marine transportation industries; and (3)
     technology licensing and consulting services for the natural gas processing
     and sulfur recovery industries.

     Historically, the two businesses described above under (1) and (2) in the
     Industrial Products Group were operated as separate divisions of Chromium
     Corporation. Effective July 1, 1999, Chromium's operations were segregated
     into separate companies. The reciprocating engine components business will
     continue to do business as Chromium Corporation (Chromium) and the digital
     wireless cellular phones and other electronic equipment business will be
     operated as subsidiaries of Cybershield, Inc. (Cybershield). The technology
     licensing and consulting services business will continue to be conducted as
     Ortloff Engineers, LTD (OEL).


                                       5
<PAGE>   7


Financial information by company segment is summarized as follows (in
thousands):

<TABLE>
<CAPTION>
                                     Three Months Ended        Nine Months Ended
                                         March 31,                 March 31,
                                   ----------------------    ----------------------
                                     2000         1999         2000          1999
                                   ---------    ---------    ---------    ---------
<S>                                <C>          <C>          <C>          <C>
SALES
Roofing products                   $  80,479    $  60,335    $ 232,248    $ 199,615
Industrial products                    9,928       10,356       35,595       28,092
Corporate and eliminations                41           44          130           95
                                   ---------    ---------    ---------    ---------
                                   $  90,448    $  70,735    $ 267,973    $ 227,802
                                   =========    =========    =========    =========
OPERATING PROFIT (LOSS)
Roofing products                   $  12,621    $   9,365    $  40,216    $  31,526
Industrial products                   (1,361)         961        1,575        3,593
Corporate and other                   (1,421)      (1,621)      (4,193)      (5,805)
                                   ---------    ---------    ---------    ---------
                                       9,839        8,705       37,598       29,314

Gain from involuntary conversion         403           --        1,292           --
Interest expense, net                   (239)        (464)        (760)      (1,468)
                                   ---------    ---------    ---------    ---------
Income before income taxes         $  10,003    $   8,241    $  38,130    $  27,846
                                   =========    =========    =========    =========

IDENTIFIABLE ASSETS
Roofing products                   $ 251,018    $ 197,602    $ 251,018    $ 197,602
Industrial products                   31,673       26,163       31,673       26,163
Corporate                             21,381       12,367       21,381       12,367
                                   ---------    ---------    ---------    ---------
                                   $ 304,072    $ 236,132    $ 304,072    $ 236,132
                                   =========    =========    =========    =========
DEPRECIATION AND AMORTIZATION
Roofing products                   $   2,122    $   1,958    $   6,333    $   5,913
Industrial products                      516          298        1,483          787
Corporate                                 38           36          114          125
                                   ---------    ---------    ---------    ---------
                                   $   2,676    $   2,292    $   7,930    $   6,825
                                   =========    =========    =========    =========
CAPITAL EXPENDITURES
Roofing products                   $  16,395    $   6,857    $  41,767    $  13,581
Industrial products                    1,452        1,143        4,831        3,791
Corporate                                639        2,174        3,218        4,864
                                   ---------    ---------    ---------    ---------
                                   $  18,486    $  10,174    $  49,816    $  22,236
                                   =========    =========    =========    =========
</TABLE>


                                       6
<PAGE>   8


8.   Basic earnings per share is computed based on the average number of common
     shares outstanding. Diluted earnings per share includes adjustments for the
     number of shares subject to outstanding stock options. The following table
     sets forth the computation of basic and diluted earnings per share (in
     thousands):

<TABLE>
<CAPTION>
                                    Three Months Ended  Nine Months Ended
                                        March 31,           March 31,
                                    ------------------  -----------------
                                      2000      1999     2000      1999
                                    -------   -------   -------   -------
<S>                                 <C>       <C>       <C>       <C>
Net income                          $ 6,211   $ 5,115   $23,691   $12,979
                                    =======   =======   =======   =======

Denominator for basic earnings
per share - weighted average
shares outstanding                   19,603    19,494    19,565    19,557

Effect of dilutive securities:
Employee stock options                  599       459       520       384
                                    -------   -------   -------   -------

Denominator for dilutive earnings
per share - adjusted weighted
average shares and assumed
issuance of shares purchased
under incentive stock option plan
using the treasury stock method      20,202    19,953    20,085    19,941
                                    =======   =======   =======   =======

Basic earnings per share            $   .32   $   .26   $  1.21   $   .67
                                    =======   =======   =======   =======

Diluted earnings per share          $   .31   $   .26   $  1.18   $   .65
                                    =======   =======   =======   =======
</TABLE>


                                       7
<PAGE>   9


ITEM 2. Management's Discussion and Analysis of Results of Operations and
Financial Condition

RESULTS OF OPERATIONS

CHANGES IN THE THREE-MONTH PERIOD ENDED MARCH 31, 2000 COMPARED TO THE
THREE-MONTH PERIOD ENDED MARCH 31, 1999.

     During the three-month period ended March 31, 2000, net income increased
21% to $6,211,000 from $5,115,000 in the three-month period ended March 31,
1999. Sales increased 28% to $90,448,000 in the current year quarter compared to
$70,735,000 in the prior year period. The increase in sales was primarily the
result of record shipments for Elk's Prestique(R) premium laminated fiberglass
asphalt shingles and roofing mat products, combined with increasing demand for
Cybershield's products used in digital wireless cellular phones. The increase in
income reflects the significant increase in sales in the roofing products
segment and income recognition from settlement of the business interruption
insurance claim. During the three-month period ended March 31, 2000, the company
recorded a $403,000 gain from involuntary conversion as a result of final
settlement on the property claim whereby the company received replacement value
payments in excess of the net book value of destroyed assets. See Note 3 on page
4 of this Form 10-Q for further information on the settlement of the business
interruption and property claims.

     Sales for the Roofing Products Group increased 33% to $80,479,000 for the
three months ended March 31, 2000 compared to $60,335,000 in the same prior year
quarter. Elk continued to benefit from strong demand for Elk's premium laminated
fiberglass asphalt shingles and its nonwoven mats used in manufacturing asphalt
roofing products and various industrial applications. Operating income increased
35% to $12,621,000 in the current year quarter compared to $9,365,000 in the
prior year quarter. The current year quarter included $1,700,000 of income
relating to the final settlement of the company's business interruption
insurance claim. However, during the third quarter of fiscal 2000, asphalt costs
were up about $3,100,000 and glass fiber costs were up about $600,000 compared
to the same prior year quarter. Elk was not able to recover these higher raw
material costs through higher prices during the current year quarter. Elk has
implemented a 4% to 5% increase in laminated shingle prices, effective March 27,
2000, and has announced a further 5% to 6% price increase, effective May 1,
2000. These price increases are expected to offset higher raw material costs,
provided that raw materials costs stabilize at current levels.

     Sales for the Industrial Products Group decreased 4% to $9,928,000 in the
current year quarter compared to $10,356,000 in the prior year third quarter.
The Industrial Products Group had an operating loss of $1,361,000 in the
three-month period ended March 31, 2000 compared to a $961,000 operating profit
in the same period last year. The reduction in sales in the current year period
and the operating loss were primarily attributable to the relocation and
consolidation of Chromium's operations to the Cleveland, Ohio facility. Chromium
was unable to fulfill demand for its remanufactured diesel engine components
used in the railroad and marine transportation industries during this period
when its facilities were being consolidated. As a result, its sales were lower
and it incurred a significant operating loss in the three-month period ended
March 31, 2000, including about $1,650,000 of nonrecurring relocation and
consolidation costs. This consolidation is expected to reduce Chromium's
operating expenses by about $1,000,000 per year.


                                       8
<PAGE>   10


     Cybershield's sales and operating profit in the three-month period ended
March 31, 2000 were adversely affected by a temporary slowdown in Cybershield's
production of digital wireless handsets in the first two months of the quarter
to make engineering changes in production systems and equipment. Cybershield
recorded a 9% increase in sales for the third quarter ended March 31, 2000 as
compared to the year-ago quarter. However Cybershield's operating profit in the
third quarter of the current year was lower than the prior year's third quarter.

     OEL, the company's patent licensing and engineering consulting services
business, reported slightly higher sales than in the prior year quarter and a
small operating loss for the three months ended March 31, 2000, as no patent
license fees were booked during the current year quarter. OEL expects to benefit
from increased demand for its services as a result of higher oil prices.

     Overall selling, general and administrative costs (SG&A) in the three-month
period ending March 31, 2000 were 12.4% higher than in the same period in the
prior fiscal year, primarily as a result of selling expenses necessary to
achieve the 28% increase in revenues. As a percentage of sales, SG&A costs were
11.1% of sales in the current year quarter compared to 12.6% in the prior year
quarter.

     Interest expense for the three months ended March 31, 2000 was lower than
in the same quarter last year. The company capitalized $748,000 of interest in
the current year quarter in connection with the construction of its new
Myerstown, Pennsylvania shingle plant and other major projects.

CHANGES IN THE NINE-MONTH PERIOD ENDED MARCH 31, 2000 COMPARED TO THE NINE-MONTH
PERIOD ENDED MARCH 31, 1999.

     During the nine-month period ended March 31, 2000, net income before last
year's cumulative effect of a change in accounting principle increased 37% to
$23,691,000 from $17,319,000 in last year's nine month period. Sales increased
18% to $267,973,000 in the current year nine-month period compared to
$227,802,000 in the prior year period. The increases in sales and net income
before the accounting change were primarily the result of strong shipments of
roofing mat products and premium laminated fiberglass asphalt shingles, combined
with increasing demand for Cybershield's products used in digital wireless
cellular phones. During the nine-month period ended March 31, 2000, the company
recorded a $1,292,000 gain from involuntary conversion as a result of payments
on the property claim whereby the company received replacement value payments in
excess of the net book value of destroyed assets. In the first quarter of fiscal
1999, the company adopted Statement of Position 98-5, "Reporting on the Costs of
Start-Up Activities," issued by the Accounting Standards Executive Committee of
the American Institute of Certified Public Accountants, which resulted in a
nonrecurring $4,340,000 charge, net of tax, for the cumulative effect of this
accounting change. This one-time cumulative charge reduced last year's
nine-month net income to $12,979,000 compared to $23,691,000 for the nine-month
period in the current fiscal year.

     Sales for the Roofing Products Group increased 16% to $232,248,000 for the
nine months ended March 31, 2000 compared to $199,615,000 in the same period
last year primarily as a result of strong demand for Elk's premium laminated
fiberglass asphalt shingles. Strong sales increases were also achieved for
nonwoven mats used in manufacturing asphalt roofing products and various
industrial applications. Operating income for the Roofing Products Group
increased 28% in the first nine months of fiscal 2000 to $40,216,000 from
$31,526,000 in the prior year period, primarily as a result of strong sales of
premium laminated fiberglass asphalt shingles and nonwoven fiberglass mats.


                                       9
<PAGE>   11


     Operating income for the nine months ended March 31, 2000 included
$3,478,000 of income relating to the company's business interruption claim
caused by an explosion at Elk's nonwoven fiberglass roofing mat plant in Ennis,
Texas in September 1998. However, in early fiscal 2000, shipments of Elk's
premium laminated fiberglass asphalt shingles were held down by lower laminated
shingle inventories. The inventory shortage was partially due to manufacturing
inefficiencies related to Elk's use of alternative sources of nonwoven
fiberglass mat in its manufacturing process as a result of the nonwoven mat
plant accident referred to above.

     Sales for the Industrial Products Group increased 27% in the first nine
months of fiscal 2000 to $35,595,000 from $28,092,000 in the same period in the
prior fiscal year. Operating income for the Industrial Products Group decreased
in the nine-month period ended March 31, 2000 to $1,575,000 compared to
$3,593,000 in the same period last year. Sales of Cybershield's advanced
shielding products and related services for the digital wireless cellular phone
industry increased 72% in the first nine months of fiscal 2000 and Cybershield's
operating profit increased 42% compared to the first nine months in the prior
fiscal year. The current year results include Cybershield's Canton, Georgia
operation, which was acquired in January 1999. This new company generated
positive operating income during the first nine months of fiscal 2000 after
incurring initial operating losses in the latter half of fiscal 1999.

     Cybershield plans to expand its digital wireless cellular phone business to
serve the European, Asian and Latin American markets over the next few years
through acquisition or other business arrangements to better serve its
customers' growing markets for digital wireless cellular phones and other
digital wireless electronic products. Cybershield is planning to establish
operations in Europe by the summer of calendar year 2000 before pursuing other
global growth opportunities.

     For the first nine months of fiscal 2000, Chromium Corporation's sales
decreased 33% compared to the same prior year period as a result of the
relocation of manufacturing facilities for remanufactured diesel engine
components used in the railroad and marine transportation industries and the
impact of the consolidation of its manufacturing operations. Primarily as a
result of about $2,600,000 nonrecurring expenses relating to the consolidation
of its manufacturing operations, Chromium recorded a significant operating loss
in the first nine months of fiscal 2000 compared to a small operating profit
achieved in the same period last year. Revenues and operating income for OEL's
patent licensing and engineering consulting services were about the same in the
first nine months of fiscal 2000 compared to the same nine-month period last
year.

     Overall SG&A costs in the nine-month period ending March 31, 2000 were
about 1% higher than in the same period in the prior fiscal year. However, in
the prior year period, the company adjusted its medical and casualty
self-insurance reserves and recorded a write-off of certain computer related
items. As a percentage of sales, SG&A costs were 11.0% of sales in the first
nine months of fiscal 2000 compared to 12.7% in the prior year period.

     Interest expense in the first nine months of fiscal 2000 was lower than in
the same period last year, as the company capitalized $1,532,000 of interest in
the current year period in connection with the construction of its new
Myerstown, Pennsylvania shingle plant and other major projects.


                                       10
<PAGE>   12


FINANCIAL CONDITION

     During the first nine months of fiscal 2000, the company generated cash
flows of $24,334,000 from operating activities. Increased working capital
requirements primarily relate to higher trade receivables and inventory levels
at March 31, 2000, which are primarily due to seasonal increases in business
activity. In addition, trade receivables generally increase during the late
winter and early spring months resulting from extended payment terms to certain
customers during these months, with payment generally due during the summer
months. Increased trade receivables and inventories were partially offset by
lower other current assets and higher current liabilities. Lower current assets
primarily reflect collections from and final settlement with an insurance
company related to the explosion at its fiberglass roofing mat plant in Ennis,
Texas in September 1998. The higher level of current liabilities was primarily
attributable to the increased levels of operating activities and payables
associated with the construction of a new roofing plant. The current ratio was
3.3:1 at both March 31, 2000 and June 30, 1999. Historically, working capital
requirements fluctuate during the year because of seasonality in some market
areas. Generally, working capital requirements and related borrowings are higher
in the spring and summer months, and lower in the fall and winter months.

     The company used $47,002,000 for investing activities in the first nine
months of fiscal 2000. Most expenditures were for additions to property, plant
and equipment. About $36,000,000 of capital expenditures in the first nine
months of fiscal 2000 were for the purchase of land and construction costs
relating to the new $70,000,000 Myerstown, Pennsylvania premium laminated
fiberglass asphalt shingle plant. This new facility is expected to be completed
in fall 2000 with manufacturing operations scheduled to begin in the December
2000 quarter. The Myerstown plant is expected to increase the company's overall
laminated shingle capacity by about 38%. The company plans to invest about
$137,000,000 over a three-year period beginning in fiscal 2000, including the
costs to build the new roofing plant, together with expenditures to expand
capacity and improve productivity at existing plants, to install production
lines for new products and to increase capacity for Cybershield's digital
wireless cellular phone business. The company expects to incur about $75,000,000
of these capital expenditures in fiscal 2000.

     Cash flows from financing activities were $23,334,000 during the first nine
months of fiscal 2000, primarily resulting from a $25,700,000 increase in
long-term debt. Long-term debt represented 36% of the $247,276,000 of invested
capital (long-term debt plus shareholders' equity) at March 31, 2000.

     In September 1998, the company's Board of Directors authorized the purchase
of up to $10,000,000 of common stock from time to time on the open market to be
used for general corporate purposes. As of March 31, 2000, 129,992 shares with a
cumulative cost of $1,771,000 had been repurchased under this authorization.

     Effective January 5, 2000, the company increased its revolving credit
facility from $100,000,000 to $125,000,000 and extended the facility to December
15, 2004 to support its capital expansion program. Management believes that
current cash and cash equivalents, cash flows from operations and its unsecured
revolving credit facility should be sufficient during fiscal 2000 and beyond to
fund its currently planned capital expenditures, working capital needs,
dividends, stock repurchases and other cash requirements. However, management
believes it could secure additional capital at favorable rates, if needed, to
support its growth and international expansion plans.


                                       11
<PAGE>   13


     The company's operations are subject to extensive federal, state and local
laws and regulations relating to environmental matters. Although the company
does not believe it will be required to expend amounts which will have a
material adverse effect on the company's consolidated financial position or
results of operations by reason of environmental laws and regulations, such laws
and regulations are frequently changed and could result in significantly
increased cost of compliance. Further, certain of the company's industrial
products operations utilize hazardous materials in their production processes.
As a result, the company incurs costs for remediation activities off-site and at
its facilities from time to time. The company establishes and maintains reserves
for such remediation activities, when appropriate. Current reserves established
for known or probable remediation activities are not material to the company's
financial position or results of operations.

YEAR 2000 ISSUE

     As of May 11, 2000, the company has experienced no significant problems
relating to its Year 2000 readiness. Activities within the company and with its
suppliers and other third parties are continuing to be monitored.

FORWARD-LOOKING STATEMENTS

This Form 10-Q contains "forward-looking statements" that involve risks and
uncertainties about its prospects for the future. The statements that are not
historical facts are forward-looking statements within the meaning of the
Private Securities Litigation Reform Act of 1995. These statements usually are
accompanied by words such as "outlook," "believe," "estimate," "plan,"
"project," "expect," "anticipate," "predict," "could," "should," "may," or
similar words that convey the uncertainty of future events or outcomes. These
statements are based on judgments the company believes are reasonable; however,
Elcor's actual results could differ materially from those discussed here. Such
risks and uncertainties include, but are not limited to, the following:

     1.   The company's roofing products business is substantially non-cyclical,
          but can be affected by weather, the availability of financing and
          general economic conditions. In addition, the asphalt roofing products
          manufacturing business is highly competitive. Actions of competitors,
          including changes in pricing, or slowing demand for asphalt roofing
          products due to general or industry economic conditions or the amount
          of inclement weather could result in decreased demand for the
          company's products, lower prices received or reduced utilization of
          plant facilities. Further, changes in building codes and other
          standards from time to time can cause changes in demand, or increases
          in costs that may not be passed through to customers.

     2.   In the asphalt roofing products business, the significant raw
          materials are ceramic coated granules, asphalt, glass fibers, resins
          and mineral filler. Increased costs of raw materials can result in
          reduced margins, as can higher trucking and rail costs. Historically,
          the company has been able to pass some of the higher raw material and
          transportation costs through to the customer. Should the company be
          unable to recover higher raw material and/or transportation costs from
          price increases of its products, operating results could be adversely
          affected and/or lower than projected.


                                       12
<PAGE>   14


     3.   The company expects to make up to $137 million in new investments to
          expand capacity and improve productivity at existing plants and to
          build new plants over a three-year period beginning in fiscal 2000.
          Progress in achieving anticipated operating efficiencies and financial
          results is difficult to predict for new plant facilities. If such
          progress is slower than anticipated, if substantial cost overruns
          occur in building new plants, or if demand for products produced at
          new plants does not meet current expectations, operating results could
          be adversely affected.

     4.   Certain facilities of the company's industrial products subsidiaries
          must utilize hazardous materials in their production process. As a
          result, the company could incur costs for remediation activities at
          its facilities or off-site, and other related exposures from time to
          time in excess of established reserves for such activities.

     5.   The company's litigation, including its trade dress litigation against
          GAF Building Materials Corporation and certain affiliates, and its
          defense of the purported class action brought by Wedgewood Knolls
          Condominium Association, is subject to inherent and case-specific
          uncertainty. The outcome of such litigation depends on numerous
          interrelated factors, many of which cannot be predicted.

     6.   Although the company currently anticipates that most of its needs for
          new capital in the near future will be met with internally generated
          funds and borrowings under its existing loan facility, significant
          increases in interest rates could substantially affect its borrowing
          costs under its existing loan facility, or its cost of alternative
          sources of capital.

     7.   Each of the company's businesses, especially Cybershield's digital
          wireless cellular phone business, is subject to the risks of
          technological changes that could affect the demand for or the relative
          cost of the company's products and services, or the method and
          profitability of the method of distribution or delivery of such
          products and services. In addition, the company's businesses each
          could suffer significant setbacks in revenues and operating income if
          it lost one or more of its largest customers, or if its customers'
          plans and/or markets should change significantly.

     8.   Although the company insures itself against physical loss to its
          manufacturing facilities, including business interruption losses,
          natural or other disasters and accidents, including but not limited to
          fire, earthquake, damaging winds and explosions, operating results
          could be adversely affected if any of its manufacturing facilities
          became inoperable for an extended period of time due to such events.

     9.   Each of the company's businesses is actively involved in the
          development of new products, processes and services which are expected
          to contribute to the company's ongoing long-term growth and earnings.
          If such development activities are not successful, or the company
          cannot provide the requisite financial and other resources to
          successfully commercialize such developments, the growth of future
          sales and earnings may be adversely affected.

     Parties are cautioned not to rely on any such forward-looking beliefs or
judgments in making investment decisions.


                                       13
<PAGE>   15


PART II. OTHER INFORMATION

ITEM 1: Legal Proceedings

GAF Patent Litigation

     On March 8, 2000, the district court in Elk's design patent case denied
GAF's motion for attorneys fees.

     Trial on Elk's trade dress claim in the design case, including GAF's
counterclaims, is unscheduled but pending. Also pending is GAF's motion for
attorneys fees in the utility patent case which was recently dismissed by
stipulation of the parties.

     While management can give no assurances regarding the ultimate outcome of
the remaining litigation, even if the outcome were to be adverse to Elk, it is
not expected to have a material adverse effect on the Registrant's financial
position or liquidity.

     For further information and background on the GAF Patent Litigation see
Part I, Item 3 of the Registrant's Annual Report on Form 10-K for the year ended
June 30, 1999, and Part II, Item 1 of the Quarterly Reports on Form 10-Q for the
quarters ended September 30, 1999 and December 31, 1999.

Wedgewood Knolls Litigation

     On February 25, 2000, Wedgewood Knolls Condominium Association filed a
purported class action against the Registrant and Elk Corporation in the United
States District Court in Newark, New Jersey. The purported nationwide class
would include purchasers or current owners of buildings with certain Elk asphalt
shingles installed between January 1, 1980 and present. The suit alleges, among
other things, that the shingles were uniformly defective. It seeks reformation
of the limited warranty applicable to the shingles, and unspecified damages for
breach of implied and written warranties and alleged unfair or deceptive trade
practices on behalf of the plaintiff and the purported class.

     The Registrant and Elk intend to vigorously defend the suit, and believe
the claims and the purported class are totally without merit.

ITEM 6: Exhibits and Reports of Form 8-K

     (a)  Exhibit:

          Exhibit (27): Financial Data Schedule (EDGAR submission only).

     (b)  The registrant filed one report on Form 8-K during the quarter ended
          March 31, 2000. The registrant filed a Form 8-K on January 20, 2000
          relating to a press release containing "forward-looking statements"
          about its prospects for the future.


                                       14
<PAGE>   16


                                   SIGNATURES


Pursuant to the requirements of the Securities and Exchange Act of 1934, the
Registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.



                                             ELCOR CORPORATION



DATE: May 11, 2000                           /s/ Richard J. Rosebery
     -----------------                       -----------------------------------
                                             Richard J. Rosebery
                                             Vice Chairman, Chief Financial &
                                             Administrative Officer

                                             /s/ Leonard R. Harral
                                             -----------------------------------
                                             Leonard R. Harral
                                             Vice President and Chief
                                             Accounting Officer


                                       15
<PAGE>   17


                                 EXHIBIT INDEX

<TABLE>
<CAPTION>
EXHIBIT
NUMBER         DESCRIPTION
------         -----------
<S>            <C>
  27           Financial Data Schedule
</TABLE>