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This paper examines the stock market reaction to 167 FDA announcements of new drug approvals during the period 1980 - 1999. Using an event study methodology, the study finds that there are significant positive abnormal returns on the day of the announcement of new drug approvals. However, there is no evidence of significant positive returns prior to the announcement. Accordingly, the paper concludes that any buying pressure arising from insiders anticipating the approval announcement does not affect the value of the stock. Significant returns do not occur until after the announcement, which is consistent with the behavior of an efficient …