To elucidate a hypotensive effect of isoptin-retard in a dose 240 mg/day, 17 males with mild and moderate hypertension receiving the drug underwent 24-h monitoring by SpaceLabs 5300 and pressure loading. A significant lowering of both mean systolic and diastolic pressure was found both in daytime and at night. A hypotensive effect persisted for 2 months. No case of serious cardiovascular complications, of noticeable shifts in blood biochemistry was reported.