We describe the background, design, and organization of a double-blind clinical trial in patients with transient ischemic attacks or nondisabling stroke in more than 60 hospitals in The Netherlands. Two different therapeutic comparisons are made by double randomization: 30 mg vs. 300 mg acetylsalicylic acid, and 50 mg atenolol vs. placebo. For the diagnosis, a checklist has been used on which the time course and the nature of the symptoms are recorded in plain language. The analysis will primarily assess death and disability from all causes, with disability measured using a modified Rankin scale. Secondary end points will be vascular death, nonfatal stroke, nonfatal myocardial infarction, and retinal infarction. The study will last for a minimum of 3 years and should involve at least 2,500 patients. More than 1,100 patients were randomized in the 1st year.