Abstract Changes in the pressure-volume relationship of the left ventricle at end-systole was investigated in moderately hypertensive patients given single doses of felodipine (n = 14, oral solution 0.05 mg/kg) or nifedipine (n = 16, sublingual capsule 10 mg). Analysis of the pressure-volume relation was a prospective aim of the study, but the decision to make a comparison between the felodipine and nifedipine groups was made retrospectively. In patients treated with felodipine or nifedipine as monotherapy, the results were qualitatively similar (ie, the reduction in systolic blood pressure was accompanied by a proportional decrease in end-systolic volume). In patients pretreated with atenolol, the response to felodipine was similar to that seen in previously untreated patients. However, after nifedipine, the decrease in systolic blood pressure was not followed by a decrease in end-systolic volume. In fact, end-systolic volume increased after nifedipine. The results indicate that nifedipine has a substantial negative inotropic effect, which is unmasked during beta-adrenergic blockade. Felodipine appears to be different and may have little or no effect on cardiac contractility.