Objective: To compare lisinopril with telmisartan, in regard to: 1) their effect on blood pressure (BP) and pulse pressure (PP), and 2) the duration and the homogeneity of their anti hypertensive effect. Patients and Methods: A randomized, open-label, crossover, comparative study of telmisartan 80 mg versus lisinopril 20 mg was conducted in 32 untreated hypertensive patients using clinic and 24-hour ambulatory BP measurements. Trough: peak ratio (TPR) and smoothness index (SI) were calculated for each drug. Results: Using both measurement techniques no difference was detected between the 2 drugs in their effects either on BP (mean difference in 24-hour systolic BP 1.2 +/- 7.1 mm Hg, 95% confidence intervals -1.4, 3.8, and diastolic 0.7 +/- 5.1, -1.2, 2.5) or on PP (0.5 +/- 3.5, -0.7, 1.8). There was no difference between the TPR and the SI values of telmisartan (TPR 0.85/0.61 for systolic/diastolic BP and SI 1.46/1.2) and lisinopril (TPR 0.74/0.64 and SI 1.3/1.17). Conclusions: These data suggest that telmisartan is as effective as lisinopril in reducing BP and PP. Both drugs seem to provide smooth and sustained effects throughout the full 24-hour period.