BACKGROUND: Despite a paucity of evidence, clinicians routinely advise that patients discontinue using nonsteroidal anti-inflammatory drugs (NSAIDs), including ibuprofen, at least 1 week before most surgical procedures. OBJECTIVE: To define the duration of ibuprofen-induced platelet dysfunction. DESIGN: Prospective cohort study. SETTING: Denver/Aurora, Colorado. PARTICIPANTS: 11 healthy adult volunteers. MEASUREMENTS: Individuals were tested at baseline and serially after completion of a 7-day course of ibuprofen (600 mg orally every 8 hours). The platelet function analyzer (PFA-100, Dade Behring, Newark, Delaware), a test that has replaced the bleeding time in many clinical settings, was used. RESULTS: All participants exhibited normal platelet function before starting ibuprofen. Platelet dysfunction was apparent after completion of the ibuprofen course in 7 of the 11 participants and normalized by 24 hours after the last ibuprofen dose. LIMITATIONS: The sample size in this study was small, and no participants had a major illness. Correlation between PFA-100 results and clinical bleeding has not been established. CONCLUSIONS: Platelet function seems to normalize within 24 hours after cessation of regular ibuprofen use in healthy individuals. Further studies are warranted to provide a rational basis for timing of NSAID withdrawal in a range of patients undergoing surgery.