Most patients inadvertently miss an occasional dose of antihypertensive therapy, and hence drugs that provide sustained blood-pressure (BP) reduction beyond the 24-h dosing interval are desirable. The primary objective of this study was to compare the 24-h mean ambulatory BP reductions from baseline after a simulated missed dose of the direct renin inhibitor aliskiren, irbesartan or ramipril. In this double-blind study, 654 hypertensive patients (24-h mean ambulatory diastolic BP (MADBP) >or=85 mm Hg) were randomized 1:1:1 to once-daily aliskiren 150 mg, irbesartan 150 mg or ramipril 5 mg. Doses were doubled after 2 weeks. At day 42, patients were again randomized equally within each group to receive 1 day of placebo ('missed dose') on either day 42 or day 49. Patients with a successful 24-h ambulatory BP measurement at baseline and on day 42/49 were included in the analyses. The 24-h mean ambulatory systolic BP (MASBP)/MADBP reductions from baseline after a missed dose of aliskiren 300 mg (9.3/7.0 mm Hg) were similar to irbesartan 300 mg (9.5/7.3 mm Hg) and significantly larger than ramipril 10 mg (7.1/5.0 mm Hg, P<or=0.008). Loss of BP-lowering effect with aliskiren in the 24 h after a missed dose (1.0/0.7 mm Hg for 24-48-h vs 0-24-h MASBP/MADBP) was significantly lower than with irbesartan (3.6/2.2 mm Hg, P<0.01) or ramipril (4.0/2.6, P<0.0001). This equates to maintenance of 91/91% of the MASBP/MADBP-lowering effect with aliskiren, greater than irbesartan (73/77%) or ramipril (64/65%). The incidence of adverse events was similar across treatments (32.9-36.0%), although ramipril treatment was associated with an increased incidence of cough (ramipril, 6.1%; aliskiren, 0.5%; irbesartan, 1.8%). Aliskiren 300 mg provided a sustained BP-lowering effect beyond the 24-h dosing interval, with a significantly smaller loss of BP-lowering effect in the 24-48 h period after dose than irbesartan 300 mg or ramipril 10 mg.