OBJECTIVE: To analyse a randomized study undertaken to compare the antihypertensive efficacy of dihydropyridine calcium antagonists in patients with essential hypertension. METHOD: Blood pressure was measured both conventionally by a doctor and by non-invasive ambulatory monitoring. RESULTS: During amlodipine therapy (5 mg once a day for 4 weeks, n = 121), the mean daytime diastolic blood pressure was lowered by 8.2+/-7.1 and 0.9+/-7.4 mmHg (means +/- SD) in patients with a pretreatment daytime diastolic blood pressure >/= 90 (n = 89) and < 90 mmHg (n = 32), respectively. In 60 (67%) among the 89 patients who had an initial daytime diastolic blood pressure >/= 90 mmHg the daytime diastolic blood pressure was lowered by >/= 5 mmHg, with a mean fall of 12.0+/- 5.2 mmHg. The decrease in daytime diastolic blood pressure averaged 0.6+/- 3.5 mmHg in the remaining non-responder patients (n = 29). CONCLUSION:It seems important to evaluate the efficacy of a given antihypertensive drug by analysing patients with white-coat hypertension separately from responders to the medication. This allows one to gain maximum information concerning the effect of therapy in the individual hypertensive patients.