1 The importance of total dose to the initial hypotensive response with an angiotensin converting enzyme inhibitor (quinapril) was assessed using a suggested 'maintenance' dose (20 mg) 27 patients entered a double-blind, randomised, crossover study of quinapril or placebo using ambulatory monitoring to assess BP response. 4 All patients remained asymptomatic and both therapy and monitoring were well tolerated. A smooth onset of antihypertensive effect was noted with an overall 24 h placebo corrected fall in systolic BP of 9.9 mmHg (7.2 -12.6 95 % CI) and diastolic BP of 6.4 mmHg (4.2-8.8) with no significant effect on heart rate. Individual placebo corrected maximal responses during the first 8 h following quinapril showed a wide range for both systolic (+1.56 to 44.0 mmHg) and diastolic (+2.3 to -35.6 mmHg) pressure. Larger falls tended to be associated with higher baseline pretreatment pressures but in no case did absolute systolic pressure fall below 100 mmHg during the first 8 h following administration of placebo or quinapril. In this relatively small study blood pressure responses were not correlated either to pretreatment plasma renin or starting blood pressure. 5 This study suggests that in uncomplicated hypertension, in the absence of sodium or volume depletion or other predisposing conditions such as cardiac failure, an excessive fall in blood pressure is unlikely to occur and therefore dosage reduction is probably unnecessary.Keywords first dose hypotension ACE inhibition quinapril essential hypertension ambulatory blood pressure recording