The possible influence of food intake on the bioavailability of one nonselective and one cardioselective beta adrenoceptor antagonist, propranolol and metoprolol, was examined by serial determinations of the drug concentrations in blood of healthy subjects, taking single doses of the drugs both on an empty stomach and together with a standardized breakfast. The results indicate that food enhances the bioavailability of both propranolol and metoprolol. They also confirm that there is extensive interindividual variation in the bioavailability of these drugs.