The long-term antihypertensive efficacy and tolerability of a fixed combination of oxprenolol 160 mg slow-release + chlortalidone 20 mg was studied in 40 out-patients with mild to moderate essential hypertension followed during one year with monthly clinical visits. The fixed combination was given at the dosage of 1 tablet once daily, in the morning, increasing to 1 tablet b.i.d. in case of lying diastolic blood pressure greater than 95 mmHg. After one year only 9 patients were on 1 tablet b.i.d., the others remaining on 1 tablet once daily regimen. Clear-cut antihypertensive effect was already evident after the 1st month of treatment. Both systolic and diastolic blood pressure further decreased after two months (p less than 0.01) showing then a constant trend to decrease till the 6th month; afterwards blood pressure values remained unchanged. Normalization of blood pressure was obtained in 63%, 73% and 80% of the patients, respectively after 1, 6 and 12 months of treatment. Laboratory data did not show significant changes. Only 3 patients complained of unwanted effects which were mild, transient and in no case compelled to interrupt the treatment. Results confirm that the fixed combination of oxprenolol 160 mg slow-release + chlorthalidone 20 mg is able to long term control mild to moderate hypertension with a good tolerability, thus allowing an improved patient compliance.