Ketanserin and calcium antagonists are frequently used for the treatment of arterial hypertension in the elderly. The possibility that combined treatment with ketanserin and the calcium antagonist nifedipine have a pro-arrhythmic effect was investigated in 20 normal volunteers aged > 60 years with normal or slightly elevated blood pressure. Each subject received monotherapy with ketanserin or nifedipine for 1 week and the combined treatment during the following week. Clinical and biochemical parameters, ECG and 24-hour ECG recording were monitored before and at the end of the first and second treatment weeks. Ketanserin and nifedipine given in monotherapy or in combination did not modify, on average, blood pressure, heart rate, the biochemical variables and the QT interval. In the 24-hour ECG recordings, 2 normal subjects developed a marked increase in the frequency of ventricular ectopics, couplets and ventricular tachycardia after combined treatment. Therefore, the present investigation does not exclude the possibility that combined treatment with ketanserin and nifedipine could increase the prevalence of arrhythmia in some elderly patients.