<PAGE>   1
                                 UNITED STATES
                       SECURITIES AND EXCHANGE COMMISSION
                             WASHINGTON, D.C. 20549

                                   FORM 10-Q

(MARK ONE)

     [X]        QUARTERLY REPORT PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

                 FOR THE QUARTERLY PERIOD ENDED MARCH 31, 1999

                                       OR

     [ ]        TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d)
                     OF THE SECURITIES EXCHANGE ACT OF 1934

               FOR THE TRANSITION PERIOD FROM _______ TO ________

                         COMMISSION FILE NUMBER 1-9859

                            PIONEER COMPANIES, INC.
             (EXACT NAME OF REGISTRANT AS SPECIFIED IN ITS CHARTER)

            DELAWARE                                  06-1215192
 (STATE OR OTHER JURISDICTION OF                   (I.R.S. EMPLOYER
  INCORPORATION OR ORGANIZATION)                   IDENTIFICATION NO.)

    4300 BANK OF AMERICA CENTER, 700 LOUISIANA STREET, HOUSTON, TEXAS 77002
                   (ADDRESS OF PRINCIPAL EXECUTIVE OFFICES)
                                   (ZIP CODE)

                                 (713) 570-3200
              (REGISTRANT'S TELEPHONE NUMBER, INCLUDING AREA CODE)




         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 [ ]

                     APPLICABLE ONLY TO CORPORATE ISSUERS:

         On April 20, 1999, there were outstanding 9,984,015 shares of the
Company's Class A Common Stock and 802,645 shares of Class B Common Stock.

<PAGE>   2

                            PIONEER COMPANIES, INC.

                               TABLE OF CONTENTS


<TABLE>
<CAPTION>
                                                                                                            Page
                                                                                                            ----
<S>          <C>                                                                                             <C>
                                       PART I--FINANCIAL INFORMATION

Item 1.      Consolidated Financial Statements

             Consolidated Balance Sheets--March 31, 1999 and December 31, 1998                                 3

             Consolidated Statements of Operations--Three Months Ended March 31, 1999 and 1998                 4

             Consolidated Statements of Cash Flows--Three Months Ended March 31, 1999 and 1998                 5

             Notes to Consolidated Financial Statements                                                        6

Item 2.      Management's Discussion and Analysis of Financial Condition and Results of Operations             8

Item 3.      Quantitative and Qualitative Disclosures About Market Risk                                       11


                                         PART II--OTHER INFORMATION

Item 6.      Exhibits and Reports on Form 8-K                                                                 11
</TABLE>







         Certain statements in this Form 10-Q regarding future expectations of
the Company's business and the Company's results of operations may be regarded
as "forward looking statements" within the meaning of the Securities Litigation
Reform Act. Such statements are subject to various risks, including the
Company's high financial leverage, the cyclical nature of the markets for many
of the Company's products and raw materials and other risks. Actual outcomes
may vary materially.


                                       2

<PAGE>   3

                         PART I -- FINANCIAL INFORMATION

                            PIONEER COMPANIES, INC.
                          CONSOLIDATED BALANCE SHEETS
                (UNAUDITED, IN THOUSANDS, EXCEPT PER SHARE DATA)

<TABLE>
<CAPTION>
                                                                                     MARCH 31,      DECEMBER 31,
                                                                                       1999            1998
                                                                                    -----------     -----------
                                    ASSETS
<S>                                                                                 <C>             <C>        
Current assets:
   Cash and cash equivalents                                                        $    40,932     $    53,822
   Accounts receivable, less allowance for doubtful accounts of $2,956 at
     March 31, 1999 and $3,122 at December 31, 1998                                      40,964          46,469
   Inventories                                                                           28,432          26,556
   Prepaid expenses                                                                       6,703           6,311
                                                                                    -----------     -----------
Total current assets                                                                    117,031         133,158
Property, plant and equipment:
   Land                                                                                  10,622          10,727
   Buildings and improvements                                                            62,680          63,455
   Machinery and equipment                                                              309,297         312,736
   Construction in progress                                                              33,420          28,357
                                                                                    -----------     -----------
                                                                                        416,019         415,275
   Less accumulated depreciation                                                        (83,463)        (76,268)
                                                                                    -----------     -----------
                                                                                        332,556         339,007
Other assets, net of accumulated amortization of $10,321 at March 31, 1999
   and $8,443 at December 31, 1998                                                       57,519          57,392
Excess cost over fair value of net assets acquired, net of accumulated
   amortization of $25,585 at March 31, 1999 and $23,271 at
   December 31, 1998                                                                    199,571         201,885
                                                                                    -----------     -----------
Total assets                                                                        $   706,677     $   731,442
                                                                                    ===========     ===========

                      LIABILITIES AND STOCKHOLDERS' EQUITY
Current liabilities:
   Accounts payable                                                                 $    28,353     $    32,288
   Accrued liabilities                                                                   34,200          33,483
   Current portion of long-term debt                                                      2,688           2,684
                                                                                    -----------     -----------
Total current liabilities                                                                65,241          68,455
Long-term debt, less current portion                                                    583,499         584,168
Accrued pension and other employee benefits                                              13,965          25,836
Other long-term liabilities                                                              20,952          23,930
Commitments and contingencies
Redeemable preferred stock: $.01 par value, authorized 10,000 shares,
   55 issued and outstanding                                                              5,500           5,500
Stockholders' equity:
   Common stock:
     Class A, $.01 par value,  authorized 46,000 shares, issued and
        outstanding:  9,959 at March 31, 1999 and 9,927 at
        December 31, 1998                                                                    99              99
     Class B, $.01 par value, authorized 4,000 shares, issued and outstanding:
        803 at March 31, 1999 and December 31, 1998, convertible
        share-for-share into Class A shares                                                   8               8
   Additional paid-in capital                                                            55,055          55,055
   Retained deficit                                                                     (37,642)        (31,609)
                                                                                    -----------     -----------
Total stockholders' equity                                                               17,520          23,553
                                                                                    -----------     -----------
Total liabilities and stockholders' equity                                          $   706,677     $   731,442
                                                                                    ===========     ===========
</TABLE>


                See notes to consolidated financial statements.


                                       3
<PAGE>   4

                            PIONEER COMPANIES, INC.
                     CONSOLIDATED STATEMENTS OF OPERATIONS
                (UNAUDITED, IN THOUSANDS, EXCEPT PER SHARE DATA)


<TABLE>
<CAPTION>
                                                                 THREE MONTHS ENDED
                                                                      MARCH 31,
                                                            ---------------------------
                                                                1999            1998
                                                            -----------     -----------
<S>                                                         <C>             <C>        
Revenues                                                    $    70,949     $   101,325
Cost of sales                                                    56,270          71,974
                                                            -----------     -----------
Gross profit                                                     14,679          29,351
Selling, general and administrative expenses                      9,911          14,086
                                                            -----------     -----------
Operating income                                                  4,768          15,265
Interest expense, net                                           (12,325)        (12,914)
Other income (expense), net                                        (996)          3,088
                                                            -----------     -----------
Income (loss) before taxes                                       (8,553)          5,439
Income tax provision (benefit)                                   (2,520)          2,663
                                                            -----------     -----------
Net income (loss)                                           $    (6,033)    $     2,776
                                                            ===========     ===========

Net income (loss) per common share:
    Basic                                                   $     (0.56)    $      0.26
                                                            ===========     ===========
    Diluted                                                 $     (0.56)    $      0.23
                                                            ===========     ===========

Weighted average number of common shares outstanding:
    Basic                                                        10,757          10,683
    Diluted                                                      10,757          11,873
</TABLE>


                See notes to consolidated financial statements.


                                       4
<PAGE>   5

                            PIONEER COMPANIES, INC.
                     CONSOLIDATED STATEMENTS OF CASH FLOWS
                           (UNAUDITED, IN THOUSANDS)

<TABLE>
<CAPTION>
                                                                            THREE MONTHS ENDED 
                                                                                 MARCH 31,
                                                                        ---------------------------
                                                                            1999            1998
                                                                        -----------     -----------
<S>                                                                     <C>             <C>        
Operating activities:
   Net income (loss)                                                    $    (6,033)    $     2,776
   Adjustments to reconcile net income (loss) to net cash
     from operating activities:
        Depreciation and amortization                                        13,249          12,123
        Net change in deferred taxes                                         (2,520)          2,923
        Reduction in post-retirement medical expense                        (12,530)             -- 
        Loss on disposals of assets                                           1,057              -- 
        Foreign exchange loss                                                  (260)           (186)
        Net effect of changes in operating assets and liabilities               828          (4,631)
                                                                        -----------     -----------
Net cash flows from operating activities                                     (6,209)         13,005
                                                                        -----------     -----------

Investing activities:
   Capital expenditures                                                      (7,270)         (4,581)
   Proceeds received from disposals of assets                                 1,143              -- 
                                                                        -----------     -----------
Net cash flows from investing activities                                     (6,127)         (4,581)
                                                                        -----------     -----------

Financing activities:
   Payments on long-term debt                                                  (665)           (654)
                                                                        -----------     -----------
Net cash flows from financing activities                                       (665)           (654)
                                                                        -----------     -----------

Effect of exchange rate changes on cash                                         111             204
                                                                        -----------     -----------
Net change in cash                                                          (12,890)          7,974

Cash at beginning of period                                                  53,822          51,887
                                                                        -----------     -----------
Cash at end of period                                                   $    40,932     $    59,861
                                                                        ===========     ===========
</TABLE>


                See notes to consolidated financial statements.


                                       5
<PAGE>   6

                            PIONEER COMPANIES, INC.
                   NOTES TO CONSOLIDATED FINANCIAL STATEMENTS
                                  (UNAUDITED)

1.  ORGANIZATION AND BASIS OF PRESENTATION

         The consolidated balance sheet at March 31, 1999 and the consolidated
statements of operations and cash flows for the periods presented are unaudited
and reflect all adjustments, consisting of normal recurring items, which
management considers necessary for a fair presentation. Operating results for
the first three months of 1999 are not necessarily indicative of results to be
expected for the year ending December 31, 1999. The consolidated financial
statements include the accounts of Pioneer Companies, Inc. ("Pioneer") and its
subsidiaries (collectively referred to as the "Company"). All significant
intercompany balances and transactions have been eliminated in consolidation.
All dollar amounts in the tabulations in the notes to the consolidated
financial statements are stated in thousands of dollars unless otherwise
indicated.

         The consolidated balance sheet at December 31, 1998 is derived from
the December 31, 1998 audited consolidated financial statements, but does not
include all disclosures required by generally accepted accounting principles,
since certain information and disclosures normally included in the notes to the
financial statements have been condensed or omitted as permitted by the rules
and regulations of the Securities and Exchange Commission. The accompanying
unaudited financial statements should be read in conjunction with the financial
statements contained in the Annual Report on Form 10-K for the year ended
December 31, 1998.

         Net income (loss) per common share is computed using the weighted
average number of common shares outstanding during the period. Per share
information for 1998 has been computed after giving retroactive effect to a 7%
stock dividend on Class A and Class B Common Stock to stockholders of record in
December 1998.

2.  SUPPLEMENTAL CASH FLOW INFORMATION

         Net effect of changes in operating assets and liabilities are as
follows:

<TABLE>
<CAPTION>
                                                                     THREE MONTHS ENDED
                                                                          MARCH 31,
                                                                ---------------------------
                                                                    1999            1998
                                                                -----------     -----------
<S>                                                             <C>             <C>
     Accounts receivable                                        $     5,951     $    10,524
     Inventories                                                     (2,121)         (3,442)
     Prepaid expenses                                                   380             623
     Other assets                                                       190            (963)
     Accounts payable                                                (4,197)        (15,130)
     Accrued liabilities                                                437           3,297
     Other long-term liabilities                                        188             460
                                                                -----------     -----------
          Net change in operating assets and liabilities        $       828     $    (4,631)
                                                                ===========     ===========
</TABLE>

     Following are supplemental disclosures of cash flow information:

<TABLE>
<CAPTION>
                                                                     THREE MONTHS ENDED
                                                                          MARCH 31,
                                                                ---------------------------
                                                                    1999            1998
                                                                -----------     -----------
<S>                                                             <C>             <C>
     Cash payments for:
        Interest                                                $     3,761     $     4,691
        Income taxes                                                    351              --
</TABLE>

Non-cash investing activity:

         In March 1999, the Company's subsidiary, Kemwater North America
Company, sold certain fixed assets. Proceeds received included cash plus a $2.5
million note receivable.


                                       6
<PAGE>   7

3.  INVENTORIES

Inventories consist of the following:

<TABLE>
<CAPTION>
                                                   MARCH 31,    DECEMBER 31,
                                                     1999           1998
                                                 -----------    -----------
<S>                                              <C>            <C>        
     Raw materials, supplies and parts           $    16,906    $    17,210
     Finished goods and work-in-process                9,638          9,045
     Inventories under exchange agreements             1,888            301
                                                 -----------    -----------
                                                 $    28,432    $    26,556
                                                 ===========    ===========
</TABLE>

4.  COMMITMENTS AND CONTINGENCIES

         The Company and its operations are subject to extensive United States
and Canadian federal, state, provincial and local laws, regulations, rules and
ordinances relating to pollution, the protection of the environment and the
release or disposal of regulated materials. The operation of any chemical
manufacturing plant and the distribution of chemical products entail certain
obligations under current environmental laws. Present or future laws may affect
the Company's capital and operating costs relating to compliance, may impose
cleanup requirements with respect to site contamination resulting from past,
present or future spills and releases and may affect the markets for the
Company's products. The Company believes that its operations are currently in
general compliance with environmental laws and regulations, the violation of
which could result in a material adverse effect on the Company's business,
properties or results of operations on a consolidated basis. There can be no
assurance, however, that material costs will not be incurred as a result of
instances of noncompliance or new regulatory requirements.

         The Company relies on indemnification from the previous owners in
connection with certain environmental liabilities at its chlor-alkali plants
and other facilities. There can be no assurance, however, that such
indemnification arrangements will be adequate to protect the Company from
environmental liabilities at these sites or that such third parties will
perform their obligations under the respective indemnification arrangements, in
which case the Company would be required to incur significant expenses for
environmental liabilities, which would have a material adverse effect on the
Company.

         The Company is subject to various legal proceedings and potential
claims arising in the ordinary course of its business. In the opinion of
management, the Company has adequate legal defenses and/or insurance coverage
with respect to these matters and management does not believe that they will
materially affect the Company's operations or financial position.

5.  EARNINGS PER SHARE

         Computational amounts for earnings per share are as follows:

<TABLE>
<CAPTION>
                                                                    THREE MONTHS ENDED
                                                                         MARCH 31,
                                                                ---------------------------
                                                                    1999           1998
                                                                -----------     -----------
<S>                                                             <C>             <C>        
Net income (loss)                                               $    (6,033)    $     2,776
                                                                ===========     ===========

Basic Earnings per Share:
    Weighted average number of common shares outstanding             10,757          10,683
                                                                ===========     ===========
    Net income (loss) per share                                 $     (0.56)    $      0.26
                                                                ===========     ===========

Diluted Earnings per Share:
    Weighted average number of common shares outstanding             10,757          10,683
    Effective of dilutive securities:
    Preferred stock                                                      --             504
    Stock options                                                        --             686
                                                                -----------     -----------
    Weighted average number of common shares outstanding,
        including dilutive securities                                10,757          11,873
                                                                ===========     ===========
    Net income (loss) per share                                 $     (0.56)    $      0.23
                                                                ===========     ===========
</TABLE>


                                       7

<PAGE>   8

ITEM 2. MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS
        OF OPERATIONS

         The following discussion and analysis should be read in conjunction
with the consolidated financial statements and the related notes thereto.

RESULTS OF OPERATIONS

THREE MONTHS ENDED MARCH 31, 1999 COMPARED TO THREE MONTHS ENDED MARCH 31, 1998

         Revenues. Revenues decreased by $30.4 million, or approximately 30%,
to $70.9 million for the three months ended March 31, 1999, as compared to the
three months ended March 31, 1998. The decrease in revenues was primarily
attributable to lower electrochemical unit ("ECU") prices. ECU prices were
approximately 36% lower during the first quarter of 1999, versus the first
quarter of 1998. Partially offsetting this decrease was a slight increase in
chlor-alkali sales volumes in 1999, as 1998 production volumes were negatively
impacted by three failed transformers, which are now fully operational.
Revenues at the Company's downstream operations decreased as the Company
disposed of its household bleach operations during the third quarter of 1998,
its pool chemicals business in the fourth quarter of 1998 and its iron
chlorides business in the first quarter of 1999. These businesses were
considered non-strategic and the Company retained supply agreements with the
purchasers.

         Cost of Sales. Cost of sales decreased $15.7 million, or approximately
22%, for the three months ended March 31, 1999, as compared to the same period
in 1998. $10.9 million of this decrease was due to the modification of the
Company's retiree health care benefits. Benefits under the plan to current
retirees were not impacted, but current employees will no longer receive
benefits under this plan. The remaining decrease in cost of sales was
principally due to lower cost of sales at the downstream subsidiaries as a
result of the disposal of the operations discussed above.

         Gross Profit. Gross profit margin decreased to 21% in 1999 from 29% in
1998, primarily as a result of the ECU pricing decrease and other items
discussed above.

         Selling, General and Administrative Expenses. Selling, general and
administrative expenses decreased by $4.2 million, or approximately 30%, for
the three months ended March 31, 1999. $1.6 million of this decrease was due to
the modification of the Company's retiree health care benefits discussed above.
The remaining decrease was primarily due to the absence of incentive
compensation accruals during 1999.

         Interest Expense, Net. Interest expense, net decreased slightly in
1999 as a result of lower interest rates in 1999, compared to 1998.

         Other Income (Expense), Net. Other income (expense), net decreased
from income of $3.1 million for the quarter ended March 31, 1998 to an expense
of $1.0 million for the quarter ended March 31, 1999. Other income in 1998
included a gain from the settlement of a lawsuit, an insurance recovery and a
state franchise tax refund. The 1999 amount was primarily a loss resulting from
the sale of the iron chlorides business in the first quarter of 1999 of $1.0
million.

         Net Income (Loss). Due to the factors described above, net loss for
the three months ended March 31, 1999 was $6.0 million, compared to a net
income of $2.8 million for the same period in 1998.

LIQUIDITY AND CAPITAL RESOURCES

         Revolving Facility. In March 1999, the Company reduced its existing
$65.0 million Revolving Facility to a $50.0 million Revolving Facility (the
"Amended Revolving Facility"). The Amended Revolving Facility provides for
revolving loans (the "Revolving Loans") in an aggregate principal amount up to
$50.0 million which includes a US$30.0 million Canadian sub-facility, and which
is also subject to borrowing base limitations. As of March 31, 1999, the
Company had the ability to draw up to approximately $30 million of additional
indebtedness, including letters of credit outstanding of $2.6 million. The
Company had no Revolving Loans outstanding at March 31, 1999.

                                       8
<PAGE>   9

         Borrowing under the Amended Revolving Facility requires a minimum
interest coverage ratio of at least 0.7 to 1.0 (0.6 from October 1, 1999 to
March 31, 2000) for the prior twelve months or on a year-to-date basis,
whichever is higher (subject to a borrowing base limitation that relates to the
level of accounts receivable). Failure to maintain a monthly coverage ratio of
1.1 to 1.0 for fifteen consecutive months would constitute an event of default.

         Financial Leverage and Covenants. As of March 31, 1999, the Company
had $586.2 million of long-term debt outstanding. While the majority of the
Company's debt is due in 2006 and 2007, the Company is required to make certain
scheduled payments each year. The degree to which the Company is indebted could
have important consequences including, but not limited to: (i) limitations on
the ability to obtain additional financing in the future for working capital,
capital expenditures, acquisitions, general corporate purposes and other
purposes, if needed; (ii) the allocation of a substantial portion of cash flow
from operations to cover cash interest requirements, thereby limiting the funds
available for operations and any future business opportunities; and (iii)
increasing the Company's vulnerability to a downturn in its business or the
economy.

         Pioneer's cash requirements include payments of interest on $11.5
million of long-term debt. Pioneer's subsidiary, Pioneer Americas, Inc.
("PAI"), is restricted in paying dividends to Pioneer or funding cash to
unrestricted subsidiaries, as defined, to the sum of $5.0 million plus 50% of
the cumulative consolidated net income of PAI since June 1997. As of March 31,
1999, no distributions were allowable under this covenant. However, the Company
believes that the existing cash balances of Pioneer and its unrestricted
subsidiaries will be sufficient to fund future required interest payments and
other cash requirements until such time that PAI's cumulative consolidated net
income is positive.

         PAI's ability to enter into new debt agreements is restricted by a
debt covenant requiring a minimum interest coverage ratio (as defined) of at
least 2.0 to 1.0 for the prior four fiscal quarters. Currently, PAI is unable
to incur additional indebtedness as a result of this covenant, other than
borrowing available under its revolving credit facility. The Company's debt
agreements contain other restrictions on PAI's subsidiaries, including the
acquisition or disposition of assets or operations.

         The Company believes that existing cash balances, cash flow from
current and anticipated future levels of operations and the availability under
the Amended Revolving Facility will be adequate to make the required payments
of principal and interest on outstanding indebtedness, as well as to fund its
future capital expenditures and working capital requirements. Annualized cash
interest of approximately $51.5 million is payable on the Company's long-term
debt. To the extent that the Company draws upon the commitments under the
revolving credit facility, due to adverse business conditions or to finance
acquisitions or for other corporate purposes, the Company's aggregate interest
expense would be increased.

         Foreign Operations and Exchange Rate Fluctuations. The Company has
operating activities in Canada and engages in export sales to various
countries. International operations and exports to foreign markets are subject
to a number of risks, including currency exchange rate fluctuations, trade
barriers, exchange controls, political risks and risks of increases in duties,
taxes and governmental royalties, as well as changes in laws and policies
governing foreign-based companies. In addition, earnings of foreign
subsidiaries and intracompany payments are subject to foreign taxation rules.

         A portion of the Company's sales and expenditures are denominated in
Canadian dollars, and accordingly, the Company's results of operations and cash
flows may be affected by fluctuations in the exchange rate between the United
States dollar and the Canadian dollar. Currently, the Company is not engaged in
forward foreign exchange contracts, but may enter into such hedging activities
in the future.

         Net Cash Flows from Operating Activities. During the first three
months of 1999, the Company had a negative cash flow of $6.2 million from
operating activities, primarily attributable to the net loss for the period,
along with a reduction in accounts payable and accrued liability balances at
March 31, 1999 compared to December 31, 1999.

         Net Cash Flows from Investing Activities. Cash used in investing
activities during the first three months of 1999 totaled $6.1 million, which
was due to capital expenditures related to property, plant and equipment,
partially offset by proceeds received from asset disposals.

         Net Cash Flows from Financing Activities. Cash used in financing
activities during the first three months of 1999 totaled $0.7 million for debt
payments.

         Working Capital. Working capital decreased to $51.8 million at March
31, 1999 from $64.7 million at December 31, 1998, a decrease of $12.9 million.
Usage of cash for operating activities and capital expenditures primarily
accounted for this 


                                       9
<PAGE>   10

decrease. Decreased accounts receivable, due to lower ECU prices, and decreased
accounts payable and accrued liabilities, caused by the timing of vendor
payments, caused offsetting changes within working capital.

YEAR 2000 ISSUES

         The Company is currently working to resolve the potential impact of
the year 2000 on the processing of date-sensitive data by the Company's
computerized information systems. The year 2000 may be critical to these
systems as many computer programs were written using two digits rather than
four to define the applicable year. As a result, any of the Company's computer
applications that have date-sensitive programs may recognize a date using "00"
as the year 1900 rather than the year 2000. This could result in system
failures in the manufacturing area that could cause serious production-related
issues. In addition, miscalculations or system failures could result in a
temporary inability to process transactions, issue invoices, remit payments,
communicate with financial institutions and other entities electronically and
update internal accounting systems. If not corrected in a timely manner, such
business disruptions would be detrimental to the continuing operations of the
Company.

         The Company has initiated a program to prepare its computer systems
and applications for the year 2000. Based on present information, management
believes that while many of the systems are already year 2000 compliant, other
systems will require modification or replacement with new programs. The Company
will utilize both internal and external resources to reprogram, replace and
test software for year 2000 compliance. The Company plans to complete the year
2000 conversion tasks by July 1999. The total project costs (including costs
spent to-date) are presently estimated not to exceed $1.0 million, to be
obtained through working capital, and will be expensed as incurred unless new
software is purchased in which case certain costs will be capitalized.

         The Company is taking steps to identify year 2000 compliance issues
that may be created by key customers, suppliers and financial institutions with
which the Company does business. While no single customer represents greater
than 10% of the Company's revenues, the Company does have several large
customers who each account for a sizable dollar amount of sales revenue. The
Company's significant vendors include electrical power companies, salt
companies and freight companies. The loss of any key customer or the inability
of any of the Company's key vendors to provide its goods and services to the
Company would have a negative impact on the Company's operations until those
entities return to normal operations.

         The anticipated future costs of the year 2000 conversion project and
the date on which the Company anticipates project completion are based on
management's best estimates, which were derived using numerous assumptions of
future events including the continued availability of certain resources, third
party modification plans and other factors. There can be no guarantee that
these estimates will be achieved and actual results could vary significantly
from current estimates.

         The Company is developing a written contingency plan which will be
completed by mid-1999 to address the issues that could arise should the Company
or any of its significant suppliers, customers or financial institutions not be
prepared to accommodate year 2000 issues timely. The Company believes that in
an emergency situation it could revert to the use of manual systems that do not
rely on computers. Through these manual systems, the Company could perform the
minimum functions required to maintain the flow of goods and provide a minimum
level of information reporting to maintain a level of control over the business
cycle. Should the Company have to utilize manual systems, it is uncertain that
it could maintain current levels of operations and this could have a material
adverse impact on the business. The Company intends to maintain constant
surveillance on the year 2000 issues and will adapt its plans as required.

ACCOUNTING CHANGES

         In June 1998, the Financial Accounting Standards Board issued
Statement of Financial Accounting Standards No. 133, "Accounting for Derivative
Instruments and Hedging Activities" ("SFAS No. 133"). SFAS No. 133 establishes
accounting and reporting standards for derivative instruments and for hedging
activities. The Company is required to adopt the provisions of SFAS No. 133 in
the third quarter of 1999. Management does not believe the adoption of the
above-mentioned accounting change will have a material effect on the Company's
financial statements.


                                      10

<PAGE>   11

ITEM 3. QUANTITATIVE AND QUALITATIVE DISCLOSURES ABOUT MARKET RISK

         The Company's market risk disclosures set forth in the Company's
Annual Report on Form 10-K for the year ended December 31, 1998 have not
changed significantly through the fiscal quarter ended March 31, 1999.


                          PART II - OTHER INFORMATION

ITEM 6. EXHIBITS AND REPORTS ON FORM 8-K


     (a)  Exhibits

            10      Amendment No. 1, dated March 29, 1999, to Amended and
                    Restated Loan and Security Agreement dated as of May 29,
                    1998, among Pioneer Americas, Inc., PCI Chemicals Canada
                    Inc., the lenders party thereto, Bank of America National
                    Trust and Savings Association, as Administrative Agent and
                    U.S. Funding Agent, and Bank America Robertson Stephens, as
                    Arranger.

            27      Financial Data Schedule.


     (b)  Reports on Form 8-K

            The Company did not file any reports on Form 8-K during the quarter
            ended March 31, 1999.


                                   SIGNATURES


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

                                         PIONEER COMPANIES, INC.




April 27, 1999                           By: /s/ Philip J. Ablove      
                                            --------------------------
                                            Philip J. Ablove
                                            Vice President and
                                            Chief Financial Officer
                                            (Principal Financial Officer)


                                      11

<PAGE>   12

                               INDEX TO EXHIBITS

<TABLE>
<CAPTION>
Exhibit
Number       Description
-------      -----------
<S>          <C>
  10         Amendment No. 1, dated March 29, 1999, to Amended and Restated Loan
             and Security Agreement dated as of May 29, 1998, among Pioneer
             Americas, Inc., PCI Chemicals Canada Inc., the lenders party
             thereto, Bank of America National Trust and Savings Association, as
             Administrative Agent and U.S. Funding Agent, and Bank America
             Robertson Stephens, as Arranger.

  27         Financial Data Schedule.
</TABLE>