This subgroup analysis from the Ticlopidine Aspirin Stroke Study (TASS) compared ticlopidine, a new antiplatelet agent, with aspirin for the prevention of recurrent transient ischemic attacks in patients who had a recent reversible cerebrovascular event. This was a multicenter, double-blind, randomized trial in patients with a recent cerebral ischemic history. Patients with a reversible cerebral ischemic event within 3 months of enrollment were eligible for the study. All patients received either aspirin 650 mg twice daily or ticlopidine 250 mg twice daily for up to 5.8 years. The primary end point in this analysis was the first occurrence of a reversible ischemic event either alone or combined with nonfatal stroke or death and fatal or nonfatal stroke. Overall, ticlopidine was better than aspirin for reducing the risk of reversible ischemic events either alone or as a composite with death and/or stroke or with fetal and/or nonfatal stroke (P = .007 to P < .001). The risk reductions with ticlopidine were maintained for the duration of the 5-year follow-up. The most frequent or clinically important adverse effects associated with ticlopidine were diarrhea, rash, and neutropenia. Neutropenia was severe in 13 patients but resolved promptly with discontinuation of therapy. The results in this subgroup of patients with reversible ischemic disease, as well as the overall analysis of TASS, suggest that ticlopidine is a more effective agent than aspirin for the prevention of recurrent transient ischemic attacks.