The aim of the present study was to compare the effects of slow-release verapamil (V), 240 mg and nitrendipine (N), 20 mg, administered once daily, on office (OBP) and 24-h ambulatory blood pressure (ABP) in patients with mild-to-moderate hypertension. Twenty patients were entered into this open, randomized, two-group (V, N) parallel study. The study groups had similar age and sex distribution. The OBP (V, 155/103 +/- 19/8 mm Hg; N, 141/98 +/- 13/4 mm Hg), heart rate (HR) (V, 74 +/- 7 beats/min; N, 77 +/- 10 beats/min), daytime systolic ABP (V, 149 +/- 14 mm Hg; N, 147 +/- 13 mm Hg), and nighttime ABP of the two groups were not statistically different after a 2-week washout period. The daytime diastolic ABP (V, 99 +/- 6 mm Hg; N, 93 +/- 6 mm Hg) was slightly lower (p less than 0.05) in group N. Both the OBP (V, 136/90 +/- 19/9 mm Hg; N, 135/85 +/- 10/4 mm Hg) and daytime ABP (V, 132/85 +/- 14/4 mm Hg; N, 136/87 +/- 13/8 mm Hg) dropped in the two groups after 8 weeks of treatment. Nonparametric analysis did not show statistical differences between the groups in OBP and ABP percentage drop. There was no significant change in nighttime ABP, HR (V, 73 +/- 10 beats/min; N, 74 +/- 12 beats/min), ECG, and laboratory exams. We conclude that both verapamil SR and nitrendipine are effective in reducing blood pressure in hypertensive patients without altering the HR.