From April 1993 to March 1994, 187 ischemic stroke patients were prospectively registered in the Hospital de Santa Maria Stroke Data Base. Demographic features, vascular risk factors, clinical symptoms and signs, computerized tomography results, the most plausible stroke mechanism, and the vascular territories affected were compared between patients with and without nausea or vomiting by univariate and multivariate statistical techniques. The same comparisons were performed in the subgroups of patients with stroke in the vertebrobasilar or carotid territory. This regression model was validated in a second sample of 102 ischemic stroke patients registered in the data base from August 1995 to April 1996. Twenty-two percent of 187 patients with ischemic stroke complained of nausea or vomiting within a 12-hour interval of stroke onset. Nausea or vomiting was more frequent in vertebrobasilar territory strokes (45%) than in carotid territory strokes (10%). In multiple regression analysis, vertebrobasilar stroke (odds ratio, OR, 3.6), headache (OR 3.1) and vertigo (OR 3.4) were significant independent predictors, while in the subgroup of patients with vertebrobasilar stroke, headache (OR 3.0) and vertigo (OR 2.5) were significant independent predictors. The identification of independent variables associated with nausea or vomiting in ischemic stroke allows the detection of patients at high risk of vomiting during the acute stroke phase and to postulate its possible pathophysiological mechanism, namely, stimulation of the vomiting center by vestibular or trigeminovascular afferents.