In a consecutive series of 984 first-ever strokes (from 1985 to 1989) in a population based study, 165 (16.7%) had lacunar infarction confirmed by CT-scan or M.R.I. The annual incidence was 35.6/100,000 in women, and 47.8/100,000 in men. Survival rates were 90% at 1 month, and 78% at 2 years. The rate of recurrent strokes was 11% at 2 years. The natural history of lacunar infarction could be drawn in this study which was population-based; 29% of lacunar infarctions are indeed not managed in hospitals. Lacunar infarctions should be identified as such in therapeutic trials since their course is clearly different from other types of strokes.