We conducted a randomized, double-blind, double-placebo study in two groups of elderly hypertensive patients aged over 60 years to compare nitrendipine to enalapril, given once daily over 4 months, as monotherapy with 20 mg tablets. Clinic blood pressure was measured monthly and 24 h ambulatory monitoring was obtained at day 0 and day 120. Fifty-two patients entered the study (22 in the nitrendipine group, 30 in the enalapril group); 4 patients in both groups were dropped from the study because they withdrew their consent to participate. Three patients under nitrendipine and five patients under enalapril were not included in the analysis of data because of insufficient follow-up. The two groups were comparable on final analysis. The clinical blood pressure was similarly reduced in both groups at 24 h postdose (172/97 to 157/85 mm Hg on nitrendipine vs. 177/98 to 154/86 mm Hg on enalapril). Seventy percent of the patients had their blood pressure normalized at the end of the study in the two groups. With ambulatory blood pressure recording, no 24 h blood pressure significant differences were found on day 120 when we calculated the mean of systolic blood pressure (SBP) or diastolic blood pressure (DBP) (137 +/- 12/82 +/- 9 mm Hg on nitrendipine vs. 136 +/- 16/82 +/- 11 mm Hg on enalapril), or for daytime or nighttime periods. The pulse pressure or the mean of the five highest SBP values was also similar in nitrendipine and enalapril patients.(ABSTRACT TRUNCATED AT 250 WORDS)