Ambulatory monitoring of BP was performed in 11 patients whose 6 suffering from systo-diastolic (group 1) and 5 from systolic hypertension only (group 2) by Pressurometer III Del Mar Avionics after placebo (P), slow release Nifedipine (srN) 20 mg b.d. and srN plus Acebutolol (A) 400 mg in the morning, administered in 3 different days according to a randomized scheme. In both group we observed a significant decrease of BP after srN during 24 hrs, but in pts. of the group 2 the reduction of systolic BP was prevalent. After administration of srN+A the decrease of BP was more consistent in both groups of pts. HR showed a reflex increase in both groups of pts. after srN, antagonized by A, especially in pts. of group 2. Variability of BP considered as difference between the min and max levels of BP during 24 hrs decreased significantly with both treatments, while variability calculated as mean of the standard deviations and as coefficient of variability did not show significant changes in both groups of pts.