An open randomized study was conducted in mild to moderate hypertensive patients to evaluate, over a 3 months treatment period, the efficacy and tolerability of carvedilol 25 mg OD and to compare, in case of insufficient results with 25 mg, the efficacy and tolerance of carvedilol 50 mg and carvedilol 25 mg coadministered with diuretics. Mean office blood pressure (sitting) of the 91 patients who completed the study according to the protocol was reduced from 161/100 to 147/91 mm Hg after 4 weeks of treatment carvedilol 25 mg OD. Continuation of carvedilol 25 mg produced no further reduction in blood pressure. Increasing carvedilol to 50 mg OD or addition of diuretics further reduced blood pressure. Ambulatory blood pressure measurements showed a significant reduction in both SBP and DBP after 3 months treatment in the three groups, as well as with respect to the circadian profile of blood pressure and heart rate. Large differences between ambulatory and office blood pressure were observed: 37% of the patients diagnosed as mild to moderate hypertensives according to office blood pressure before treatment had mean daytime DBP < 90 mm Hg and 39% mean daytime SBP < 140 mm Hg. Twenty-eight percent of the patients experienced adverse events; they occurred mainly at the beginning of treatment; less than 5% of participants withdrew due to adverse events. The most frequent adverse events were fatigue, vertigo and asthenia. This study showed that carvedilol is safe and effective in the treatment of mild to moderate hypertension and that there is a high prevalence (nearly 40%) of low ambulatory blood pressure means in a population labelled as mild to moderate hypertensive.