The Persantine Aspirin Trial is a double-blind multi-centered cooperative study focusing primarily on the question of whether the administration of the combination of aspirin and dipyridamole (Persantine) will result in a greater reduction of cerebral or retinal infarction or death than the administration of aspirin alone. Fifteen centers in the United States and Canada are participating. More than 750 individuals with a history of recent carotid territory transient ischemic attacks (TIAs) have been admitted over the past four years and randomly allocated to either aspirin (325 mg) plus placebo four times daily or aspirin (325 mg) plus Persantine (75 mg) four times daily. It is anticipated that the study will continue through 1983. Analysis and publication of results are planned for 1984.