The acute subject-rated, performance-impairing, and physiological effects of ethanol (0, 0.5, and 1 g/kg) were examined after pretreatment with isradipine (0, 5, and 10 mg) in nine healthy volunteers. Volunteers received 1 of the 9 ethanol-isradipine combinations during each of nine experimental sessions. Ethanol alone produced prototypical subject-rated drug effects (e.g., increased ratings of "Drunk," "Good effects," and "Like drug") and impaired performance. Isradipine alone also produced significant subject-rated drug effects (e.g., increased ratings of "Drug effect," "Bad effects," "High," and "Stimulated"), but did not impair performance. Isradipine pretreatment generally did not significantly alter the subject-rated or performance-impairing effects of ethanol. Isradipine alone, but not ethanol alone, significantly decreased systolic and diastolic blood pressure. The ethanol-isradipine combinations generally produced significantly greater decreases in blood pressure than were observed with isradipine alone. Breath-alcohol levels were significantly lower after isradipine pretreatment, which suggests isradipine altered the bioavailability of ethanol. The present findings extend previous studies with humans that examined the behavioral effects of ethanol after pretreatment with other calcium-channel blockers, including nifedipine, nimodipine, and verapamil. Whereas the available studies suggest that calcium-channel blockers would not be useful pharmacological adjuncts in the management of ethanol abuse, more research is needed. Future studies should use self-administration and drug discrimination procedures adapted for use with humans to determine if calcium-channel blockers can attenuate any of the behavioral effects of ethanol.