Management strategies for optimal stroke prevention depend on the cause of threatened stroke. We know relatively little about the etiology of stroke in Mexican Americans, who make up one quarter of the population in Texas. A retrospective case series of 159 consecutive patients hospitalized in San Antonio, Tex, for acute, first-ever stroke compared risk factors, features, and causes of stroke between Mexican Americans and whites. Mexican Americans who had strokes were significantly younger than whites and had diabetes mellitus more often. Intracerebral hemorrhage and lacunar infarcts occurred often in Mexican Americans. Ethnicity appeared to be an independent risk factor for lacunar infarction. Mortality and functional outcome at the time of hospital discharge were similar in Mexican Americans and whites. Intrinsic small-vessel disease causing lacunar infarcts and intracerebral hemorrhage accounts for about one half of strokes in Mexican Americans. Stroke among Mexican Americans in South Texas has a distinctive profile with implications for its prevention.