<PAGE>




                  SECURITIES AND EXCHANGE COMMISSION
                        WASHINGTON, D.C. 20549

                              FORM 10-QSB
(Mark One)

         /x/  Quarterly Report Pursuant to Section 13 or 15(d) of the Securities
              Exchange Act of 1934

                  For the quarterly period ended July 31, 1997

                                  or

         / /  Transition Report Pursuant to Section 13 or 15(d) of the 
              Securities Exchange Act of 1934


                    Commission file number  0-26670

                    NORTH AMERICAN SCIENTIFIC, INC.
         (Name of small business as specified in its charter)

         Delaware                                     51-0366422
(State or other jurisdiction of            (I.R.S. Employer Identification No.)
incorporation or organization)


    7435 Greenbush Avenue
    North Hollywood, CA                                  91605    
(Address of principal executive offices)               (Zip Code) 



            Issuer's telephone number, including area code:
                            (818) 503-9201



    Check whether the issuer (1) filed all reports required to be filed by
Section 13 or 15(d) of the Exchange Act during the past 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
    ---     ---

    At September 10, 1997,  there were 3,350,201 shares of the registrant's
common stock outstanding.


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                    NORTH AMERICAN SCIENTIFIC, INC.

                   THIRD QUARTER ENDED JULY 31, 1997




DESCRIPTION                                                                 PAGE
-----------                                                                 ----

PART I   FINANCIAL INFORMATION


         Item 1.   Consolidated Financial Statements

                   CONSOLIDATED BALANCE SHEET                                1
                     July 31, 1997 and October 31, 1996

                   CONSOLIDATED STATEMENT OF OPERATIONS                      2
                     Nine months and Three months ended July 31, 1997
                     and July 31, 1996

                   CONSOLIDATED STATEMENTS OF CASH FLOWS                     3
                     Nine months ended July 31, 1997 and July 31, 1996

                   NOTES TO FINANCIAL STATEMENTS                             4

          Item 2.  Management's Discussion and Analysis of Financial         5
                   Condition and Results of Operations


PART II    OTHER INFORMATION                                                 6


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                    NORTH AMERICAN SCIENTIFIC, INC.

                      CONSOLIDATED BALANCE SHEET


                                ASSETS


                                                       October 31,  July 31,
                                                          1996        1997
                                                          ----        ----
                                                                   (unaudited)

Current assets:
    Cash and cash equivalents                        $   866,000   $ 1,887,000
    Investments                                           26,200        26,900
    Accounts receivable, less allowance for doubtful
     accounts of $0 and $4,500, respectively             683,200       467,700
    Inventories                                          144,800       380,300
    Prepaid expenses and other current assets             22,500        75,000
                                                     -----------   -----------

        Total current assets                           1,742,700     2,836,500

Equipment and leasehold improvements, net                215,900       329,900
Deposits and other assets                                 41,600        54,300
                                                     -----------   -----------

                                                     $ 2,000,200   $ 3,221,100
                                                     -----------   -----------
                                                     -----------   -----------


                 LIABILITIES AND STOCKHOLDER'S EQUITY

Current liabilities:
    Accounts payable                                 $   272,600   $   319,500
    Accrued expenses                                      43,800        40,900
    Income taxes payable                                 155,400             -
                                                     -----------   -----------

        Total current liabilities                        471,800       360,400


Stockholder's equity:
    Preferred stock, par value $.01 per share;
     authorized 2,000,000 shares, no shares issued             -             -
    Common stock, par value $.01 per share; authorized
     10,000,000 shares; 1997 - 3,323,301 shares issued
     and outstanding, 1996 - 2,983,201 shares issued
     and outstanding                                      29,800        33,200
    Additional paid-in capital                         2,105,100     3,220,000
    Accumulated deficit                                 (597,100)     (376,900)
    Cumulative translation adjustment                     (9,400)      (15,600)
                                                     -----------   -----------

        Total stockholder's equity                     1,528,400     2,860,700
                                                     -----------   -----------

                                                     $ 2,000,200   $ 3,221,100
                                                     -----------   -----------
                                                     -----------   -----------


     See accompanying notes to consolidated financial statements.


                                   1
<PAGE>

                    NORTH AMERICAN SCIENTIFIC, INC.

                 CONSOLIDATED STATEMENT OF OPERATIONS
                              (unaudited)


<TABLE>
<CAPTION>

                                                 Nine Months Ended            Three Months Ended
                                                      JULY 31,                     July 31,
                                                -------------------           -------------------
                                                1997           1996           1997           1996
                                                ----           ----           ----           ----

<S>                                         <C>            <C>            <C>            <C>
Net sales                                   $2,589,500     $2,030,600     $  820,400     $  836,300
Cost of goods sold                           1,367,100      1,024,500        449,100        417,700
                                            ----------     ----------     ----------     ----------

      Gross profit                           1,222,400      1,006,100        371,300        418,600

Research and development expenses               28,400          9,500         13,400            600
General and administrative expenses            851,300        574,200        296,300        218,800
                                            ----------     ----------     ----------     ----------

      Income from operations                   342,700        422,400         61,600       199,200


Interest and other income                       32,000         15,400         16,200          4,800
                                            ----------     ----------     ----------     ----------

    Income from continuing operations
     before income taxes                       374,700        437,800         77,800        204,000


Income taxes                                   154,500        176,300         36,600         88,200
                                            ----------     ----------     ----------     ----------

    Net income for period                   $  220,200     $  261,500     $   41,200     $  115,800
                                            ----------     ----------     ----------     ----------
                                            ----------     ----------     ----------     ----------

Earnings per share:

    Net earnings per share                  $      .07     $      .09     $      .01     $      .04
                                            ----------     ----------     ----------     ----------
                                            ----------     ----------     ----------     ----------

Weighted average number of shares
outstanding                                  3,078,757      2,983,201      3,194,868      2,983,201
                                            ----------     ----------     ----------     ----------
                                            ----------     ----------     ----------     ----------

</TABLE>

     See accompanying notes to consolidated financial statements.

                                   2
<PAGE>

                    NORTH AMERICAN SCIENTIFIC, INC.

                 CONSOLIDATED STATEMENT OF CASH FLOWS
                              (unaudited)

                                                               Nine Months
                                                              Ended July 31,
                                                            -----------------
                                                            1997         1996
                                                            ----         ----

Cash flows from operating activities:
  Net income                                          $  220,200   $  261,500
  Adjustments to reconcile net income to
    net cash used in operating activities:
      Depreciation and amortization                       38,900       35,100
      Changes in assets and liabilities:
       Accounts receivable                               215,500      (95,500)
       Inventories                                      (235,500)     (26,600)
       Prepaid expenses and other current assets         (52,500)     (12,200)
       Deposits and other assets                         (12,700)      (1,900)
       Accounts payable                                   46,900      116,900
       Accrued expenses                                   (2,900)      (9,000)
       Income taxes payable                             (155,400)      50,200
                                                      ----------   ----------

       Total adjustments                                (157,700)      57,000
                                                      ----------   ----------

  Net cash provided by operating activities               62,500      318,500


Cash flows from investing activities:
  Purchase of fixed assets                              (151,000)    (131,400)
                                                      ----------   ----------

    Net cash used for investing activities              (151,000)    (131,400)

Cash provided by financing activities:
    Issuance of common shares                          1,114,600            -

Effect of foreign exchange on cash                        (5,100)     (10,000)
                                                      ----------   ----------

Net increase in cash and cash equivalents              1,021,000      177,100

Cash and cash equivalents, beginning of period           866,000      491,000
                                                      ----------   ----------

Cash and cash equivalents, end of period              $1,887,000   $  668,100
                                                      ----------   ----------
                                                      ----------   ----------

Supplemental disclosure of cash flow information:

  Interest paid                                       $      800   $      600
                                                      ----------   ----------
                                                      ----------   ----------

  Income taxes paid                                   $  344,000   $  126,100
                                                      ----------   ----------
                                                      ----------   ----------


     See accompanying notes to consolidated financial statements.


                                   3
<PAGE>

                    NORTH AMERICAN SCIENTIFIC, INC.


              NOTES TO CONSOLIDATED FINANCIAL STATEMENTS



NOTE 1 - ORGANIZATION AND SUMMARY OF
 SIGNIFICANT ACCOUNTING POLICIES:

North American Scientific, Inc. manufactures and distributes a line of low-level
radiation sources and standards for medical, scientific, and industrial uses.
References to the "Company" include both the parent company and its subsidiary.

BASIS OF PRESENTATION

The consolidated financial statements have been prepared by North American
Scientific, Inc. (the "Company"), without audit, pursuant to the rules and
regulations of the Securities and Exchange Commission (the "Commission").
Certain information and footnote disclosures normally included in financial
statements prepared in accordance with generally accepted accounting principles
have been condensed or omitted pursuant to such rules and regulations, although
the Company believes that the disclosures are adequate to make the information
not misleading.  These financial statements should be read in conjunction with
the financial statements and related notes contained in the Company's 1996
Annual Report.  Other than as indicated herein, there have been no significant
changes from the data presented in said Report.

In the opinion of management, the financial statements contain all adjustments
necessary to present fairly the financial position of the Company as of July 31,
1997 and July 31, 1996, and the results of operations and cash flows for the
same periods.

INVENTORIES

Inventories are valued at the lower-of-cost or market.  Cost is determined using
the first-in-first-out method.

RECLASSIFICATION

Certain reclassifications of previously reported amounts have been made to
conform to the current year's presentation.


                                   4
<PAGE>

MANAGEMENT'S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF
OPERATION

    The following discussion should be read in conjunction with the
consolidated financial statements contained herein and the notes thereto.
Certain matters discussed in this Report on Form 10-QSB are forward looking as
that term is defined by: (i) the Private Securities Litigation Reform Act of
1995 (the "Act") and (ii) releases made by the Commission.  These statements are
being made pursuant to the provisions of the Act and with the intention of
obtaining the benefits of the "safe harbor" provisions of the Act.  The Company
cautions investors that any forward looking statements made by the Company are
not guarantees of future performance and that actual results may differ
materially from those in such forward looking statements as a result of various
factors, including but not limited to the following: changing market conditions;
the availability and cost of raw materials; the timing of customer's orders; the
timely development and market acceptance of the Company's products; the impact
of competitive products and pricing; and other risks detailed herein or detailed
from time to time in the Company's filings with the Commission.


THREE AND NINE MONTH PERIODS ENDED JULY 31, 1997 COMPARED WITH THREE AND NINE
MONTH PERIODS ENDED JULY 31, 1996

    Net sales decreased to $820,400 for the 1997 three month period from
$836,300 for the 1996 period under review, a  decrease of approximately 2%.  The
reduction in net sales was principally the result of a delay in shipment of
approximately $100,000 of product due to delays in receipt of certain  customer
supplied shielded assemblies necessary for shipment.  This delay was not
controllable by the Company and has since been corrected.  Although the Company
believes this specific problem will not recur, there can be no assurance that
similar delays will not be experienced in the future.  The Company anticipates
recognition of income from this delayed sale of product in the fourth quarter of
the fiscal year.  Net income decreased to $41,200, or $0.01 per share, in the
1997 period, from a net income of $115,800, or $0.04 per share in the 1996 three
month period.  Net sales for the first nine months increased to $2,589,500 for
the 1997 period from $2,030,600 for the 1996 period, an increase of
approximately 28%.  Net income for the first nine months decreased to  $220,200,
or $0.07 per share, in the 1997 period, from a net income of $261,500, or $0.09
per share, in the 1996 period, a decrease of approximately 16%.

    For the third quarter, cost of goods sold increased to $449,100 in 1997 
from $417,700 in the 1996 fiscal period, an increase of approximately 8%.  
For the nine month period comparison, cost of goods sold increased to 
$1,367,100 in 1997 from $1,024,500 in the 1996 fiscal period, an increase of 
approximately 33%.  While a portion of this increase was generally consistent 
with the increase in net sales, the Company did experience a relative 
increase in sales of certain relatively higher costs nuclide product lines. 
The Company also experienced costs associated with certain development 
efforts undertaken in the second quarter.

    For the third quarter, general and administrative expenses increased to 
$296,300 in 1997 from $218,800 in the 1996, an increase of approximately 35%. 
For the nine month comparison, general and administrative expenses increased 
to $851,300 in 1997 from $574,200 in the 1996 fiscal period, an increase of 
approximately 48%.  The increase in general and administrative expenses in 
the third quarter was primarily the result of promotional expenses and 
professional fees, including fees associated with the Company's agreements 
with Mentor Corporation ("Mentor"), which provide for the investment of an 
aggregate of $3 million in Common and Preferred Stock of the Company by 
Mentor and for Mentor to distribute I-125 brachytherapy sources to be 
manufactured by the Company.  Increased expenses for the nine month fiscal 
1997 period were primarily the result of legal expenses associated with the 
Company's defense of a lawsuit which was voluntarily dismissed by the 
plaintiff earlier in this fiscal year; the expenses associated with the 
Mentor agreements described above; and one time professional fees associated 
with new technical sales literature.

                                   5
<PAGE>

LIQUIDITY AND CAPITAL RESOURCES

    At July 31, 1997, the Company had cash and short-term deposits aggregating
approximately $ 1,887,000, compared to $ 668,100 at July 31, 1996.  The increase
in the Company's cash position was primarily the result of a $1 million
investment by Mentor in the Company's Common Stock.  To date, the Company's
short-term liquidity needs have generally consisted of operating capital to
finance growth in trade accounts receivable, inventories, and new product
development.  The Company has satisfied these needs primarily through a
combination of private and public equity financings and from cash generated by
operations.  The Company has no long-term debt and has not had, or had the need
for, a line of credit or similar arrangement with a bank.  Management
anticipates that the Company's continued growth will be funded from operations
or sales of securities and believes that it will continue to have sufficient
cash resources from such sources to fund its cash needs.

    For the nine month period ended July 31, 1997, cash flow from operations
generated approximately $ 62,500, compared to $ 318,500 for the comparable 1996
period.  Cash flow in investing activities used approximately $ 151,000 in the
1997 fiscal period compared to $ 131,400 in the comparable 1996 period.  The
increased use of cash for investing activities in the current period resulted
primarily from equipment purchases associated with the Company's I-125
brachytherapy source line for treatment of prostate cancer, which will be
marketed by Mentor.




                      PART II   OTHER INFORMATION


The Company was not required to report the information pursuant to Items 1
through 6 of Part II of Form 10-QSB for any of the three months ended July 31,
1997, except as follows:

ITEM 2.     CHANGES IN SECURITIES

c)  On June 16, 1997, the Company issued 250,000 shares of its Common Stock, 
par value $0.01 per share, to Mentor, pursuant to the Stock Purchase 
Agreement attached hereto as Exhibit 10.1, at a price of $4.00 per share.  
The issuance of such shares was exempt under the Securities Act of 1933, as 
amended, pursuant to Section 4 (2) thereof, as a transaction not involving a 
public offering.

ITEM 6.     EXHIBITS AND REPORTS ON FORM 8-K

a)  Exhibits - The following Exhibits are filed herewith:

       Exhibit 10.1 - Stock Purchase Agreement dated as of June 16, 1997 between
                       the Registrant and Mentor Corporation.

       Exhibit 10.2 - Exclusive Marketing and Distribution Agreement dated as of
                      June 16, 1997 between the Registrant and Mentor 
                      Corporation.

       Exhibit 27 - Financial Data Schedule (EDGAR only)

b)  Reports on Form 8-K - No such reports were filed during the quarter for
which this report is filed.


                                   6
<PAGE>

                              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 thereunto duly authorized.



                                 NORTH AMERICAN SCIENTIFIC, INC.
                                          (Registrant)



Date   September 10, 1997         By:      \s\  L. Michael Cutrer
    ----------------------------     ----------------------------------------
                                  L. Michael Cutrer
                                  President and Chief Executive Officer
                                  (Principal Executive, Accounting and
                                  Financial Officer)


                                   7