BACKGROUND: It has been proposed that most prognostic factors in patients with transient ischemic attack or nondisabling stroke are weak and consequently that patients at high risk of recurrent major vascular events cannot be reliably identified. METHODS: In the Dutch TIA trial, a multicenter, double-blind study of low-dose versus medium-dose aspirin, 3127 patients were included within 3 months after onset of a transient ischemic attack, amaurosis fugax, or nondisabling stroke. In a previous analysis, we developed a prediction model by means of Cox proportional hazards regression for the composite outcomes of fatal or nonfatal stroke and for myocardial infarction, stroke, or vascular death, based on clinical and demographic information as well as on the results of ancillary investigations. We assessed the discriminatory power and the calibration of the prediction models. RESULTS: The median numbers of prognostic factors for stroke, myocardial infarction, or vascular death outcome and for stroke alone were 3 and 4, respectively. The proportion of patients with a predicted probability exceeding 30% was less than 5% for both models; here the calibration of the models was poor. Only four of the patients with stroke, myocardial infarction, or vascular death were assigned a probability of greater than 50% for that outcome, and only one of the patients with stroke was given such a high probability. The models' discriminatory abil