Platelet suppressant drugs have been suggested as beneficial for patients with transient cerebral ischemic attacks and these drugs have been shown to lengthen shortened platelet survival time. In the present study platelet survival time (autologous labeling with 51Chromium) was measured in 25 patients with transient cerebral ischemia involving a carotid distribution. Platelet survival was shortened in all patients (2.5 +/- 0.10 days; AVE t 1/2 +/- SEM; Normal 3.7 +/- 0.04 days P less than 0.001). Sulfinpyrazone increased platelet survival in 9 of 19 (47%) of patients (2.4 +/- 0.10 to 2.8 +/- 0.16 days; P less than 0.01). Of the 19 treated with sulfinpyrazone, 10 had a marked reduction in the frequency of transient ischemic episodes and an increased in platelet survival (2.6 +/- 0.16 to 3.1 +/- 0.22 days; P less than 0.01) was observed in all patients. Three patients had no benefit from sulfinpyrazone and alteration of platelet survival did not occur. Results suggest that platelet survival is shortened in patients with transient cerebral ischemia, that sulfinpyrazone increases platelet curvival and may decrease the frequency of ischemic episodes, and that there may be a relationship between clinical benefit and alteration of platelet survival time.