Self-assessment of blood pressure and ambulatory blood pressure monitoring (ABPM) are being more widely used in the diagnosis and therapy of hypertension, in addition to office blood pressure measurement. The present multicenter double-blind study compared cilazapril 2.5 to 5 mg (n = 26) to atenolol 50 to 100 mg (n = 27) over a period course of eight weeks. Office blood pressures in the morning before medication, ABPM over 24 h and self assessment of the blood pressure in the morning and evening were taken. The aim of the study was to find out if the results of ABPM and self assessment of blood pressure are similar when compared to office blood pressure measurement. After four weeks of therapy both cilazapril and atenolol achieved a significant and comparable reduction of blood pressure, which did not change significantly afterwards. Both medications showed a comparable blood pressure control over 24 h. with a once-a-day regimen. The comparison of the three techniques of blood pressure measurement demonstrates that ABPM results in significantly lower average daily values than office blood pressure measurement and that the self-assessed blood pressure values in most cases lie in-between. Although the diastolic ambulatory daily values were on the average 9 mmHg lower than the corresponding office values, it was not possible for an individual patient to accurately predict the ambulatory value obtained by to his office blood pressure value. Similar results were found for the values according to self assessment of blood pressure.(ABSTRACT TRUNCATED AT 250 WORDS)