Biotechnology stock indexes ended the week down on Friday,giving up some of the modest gains they posted earlier in theweek.

The overall market sagged in the slowest trading day of theyear prior to the beginning of the three-day Labor Day holiday.Big Board volume for the day was an estimated 124.34 millionshares, down from 212.54 million the previous session. TheDow Jones industrial averages dropped 10.27 points to close at3,281.93, finishing the week with a net gain of 14.32 points.

The Chicago Board Options Exchange (CBOE) index of 20 biotechstocks fell 1.60 on Friday to close at 138.22, up from its low forthe week on Monday of 133.98.

The AMEX Biotechnology Index of 15 stocks also dropped onFriday to end the week at 144.59 After falling to the 142.74level Monday, the index inched up 1.34 points on Monday and1.23 points the next day.

Among the most active biotech issues on Friday were ChironCorp. (NASDAQ:CHIR), which closed down $1.75 a share to endthe week where it started at $49.50. Aphton Corp. (APHT),which closed as high as $19.50 a share last Monday, continueda retreat on Friday to close at $16.25, down $1.

Among the gainers for the week was Genelabs TechnologiesInc. (GNLB), which announced last Thursday a researchcollaboration with SmithKline Beecham to develop a hepatitis Evaccine. It closed last Friday at $5.88 a share, unchanged forthe day but up 75 cents for the week.

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