In one multicenter, double-blind study, 659 hypertensive patients were treated for 16 weeks with either nilvadipine (n = 326) or nifedipine (n = 333). The major objective of the study was to compare the compatibility of the two calcium antagonists with regard to hepatic compatibility and side-effect profiles. The dosages were chosen so that the effective blood pressure reduction in both groups was equally good (mean decreases in systolic pressure of 27 +/- 12 mm Hg with nilvadipine and 26 +/- 15 mm Hg with nifedipine, and in diastolic pressure of 18 +/- 6 mm Hg with nilvadipine and 19 +/- 7 mm Hg with nifedipine). The mean heart rate was slightly lowered by about 2 beats/min by both substances. Although there was no effect on lipid or glucose levels, the serum glutamate-pyruvate transaminase (SPGT) levels were more often found to be raised in the nifedipine group than in the nilvadipine group (p < 0.05). The vasodilator effect of both calcium antagonists was responsible for side effects, of which the most common were flushing, edema, headache, and palpitations. The number of complaints was less in the group treated with nilvadipine than with nifedipine, especially flushing and edema. Significantly more patients in the nifedipine group withdrew from treatment due to undesirable side effects (p < 0.05).