Background and Purpose This study was undertaken to determine factors of importance for the development of leukoaraiosis and to evaluate whether leukoaraiosis influences stroke outcome. Methods The study was prospective and consecutive and included 1084 unselected patients with acute stroke and transient ischemic attack admitted from the community of Bispebjerg (Copenhagen, Denmark) during a 25-month period from September 1, 1991, to September 30, 1993. All patients were treated in a stroke unit from the time of acute admission to completion of rehabilitation. Daily alcohol consumption and other putative risk factors were registered on admission, and patients were evaluated weekly to death or time of completed rehabilitation by means of neurological (Scandinavian Stroke Scale) and functional (Barthel Index) scores. Leukoaraiosis was diagnosed on computed tomographic scan. Multivariate analyses were applied to test relations independent of other influencing factors. Results Leukoaraiosis was present in 15% of the patients. Age was the only factor that significantly increased the risk of leukoaraiosis (odds ratio [OR] per 10-year increase, 2.4; 95% confidence interval [CI], 1.8 to 3.1), whereas the presence of atrial fibrillation was adversely related to leukoaraiosis (OR, 0.26; 95% CI, 0.13 to 0.52). Moderate daily alcohol consumption (1 to 5 drinks) reduced the risk of leukoaraiosis (OR, 0.50; 95% CI, 0.28 to 0.87), whereas heavy daily alcohol consumption (>5 drinks) tended to increase the risk (OR, 1.3; 95% CI, 0.5 to 3.3). Leukoaraiosis was not related to the presence of hypertension, diabetes, ischemic heart disease, atrial fibrillation, intermittent claudication, smoking, or sex. The presence of leukoaraiosis had no influence on neurological outcome ( P =.20), functional outcome ( P =.47), length of hospital stay ( P =.75), or mortality ( P =.31). Conclusions Moderate daily alcohol intake seems associated with a decreased risk of leukoaraiosis in stroke patients. The relation between alcohol intake and leukoaraiosis may even be U-shaped, like the relation between alcohol intake and coronary heart disease, alcohol intake and mortality, and alcohol intake and stroke. The presence of leukoaraiosis does not seem to influence the rehabilitation process or outcome of stroke.