The Ticlopidine Aspirin Stroke Study (TASS) and the Canadian-American Ticlopidine Study (CATS) were established by the Syntex Corporation to evaluate the potential efficacy of the antiplatelet agent ticlopidine. TASS was designed to address the use of the drug in the prevention of stroke in patients who had been diagnosed as having had one or more transient ischemic attacks (TIAs), using aspirin as a positive control. CATS was designed as a placebo-controlled trial to evaluate the drug's usefulness in prevention of a second stroke in patients after an initial stroke. Both studies were established in a "triple-blind" fashion where the patients, investigators, and Syntex were unaware of the patient assignments as to ticlopidine or control. In order to monitor the studies for potential toxicity/efficacy, Syntex established a "Safety Committee." The presentation describes, from the viewpoint of the Safety Committee, some of the issues raised by the results as they developed, by the investigators, the company, and the regulatory authorities involved. The decisions reached are discussed along with the rationale for those decisions and the outcomes.