Clarithromycin is a relatively new macrolide antibiotic that offers twice-daily dosing. It differs from erythromycin only in the methylation of the hydroxyl group at position 6. Although the side-effect profile of erythromycin is established, including gastroenteritis and interactions with other drugs subject to hepatic mixed-function oxidase metabolism, experience with the newer macrolides is still being recorded. Cardiotoxicity has been demonstrated after both intravenous and oral administration of erythromycin but has never been reported with the newer macrolides. We report a case of ventricular dysrhythmias that occurred after six therapeutic doses of clarithromycin. The dysrhythmias resolved after discontinuation of the drug.