A pharmacological model of alcoholism in rats was developed by administering ethanol in their drinking water. This model has provided us with a convenient means to study the effects of chronic ethanol consumption on cardiac functional properties. Our "treated" animals consumed, on the average, an equivalent of 11.1 g/kg of absolute ethanol per day and had an average blood ethanol concentration of 26.9 mg/dL at the end of the 12-week treatment period. The Langendorff-perfused hearts from both treatment and control groups performed equally well mechanically when left to beat spontaneously, but under conditions of electrical pacing the contractile ability of hearts from the alcohol-treated animals deteriorated more rapidly. Dose-response relationships for isoproterenol (isopropylnoradrenaline, IPNA) showed that hearts from alcohol-treated animals did not respond as well as hearts from control animals at higher doses of IPNA. This trend was completely reversed in the presence of low external calcium where the hearts from alcohol-treated animals responded better at all IPNA concentrations. Our observations suggest that chronic alcohol consumption may give rise to alterations in calcium ion handling at the level of myocardial plasma membranes.