Nebivolol has been adequately tested in clinical efficacy trials of patients with mild hypertension. Clinical efficacy trials or their meta-analyses did not accurately predict the outcome of subsequent large studies. The primary objective was to assess the efficacy/safety of nebivolol 5-10 mg daily in a nationwide study of patients with mild hypertension. Secondary objectives were (1) to compare efficacy/safety as monotherapy versus add-on therapy and (2) to assess the effect of nebivolol on ISH. This was an open-label, 6-week follow-up study of 6,356 patients with mild hypertension or ISH, as defined by the 1999 World Health Organization guidelines, recruited from 2,700 facilities. Previous monotherapies were continued except for beta-blockers. Results are reported as means+/-SDs. Intention-to-treat analysis is given. A total of 5,740 patients completed the study; of the withdrawals, 90% were lost for follow-up or were noncompliant, 38% were untreated before, 23% had beta-blockers. In the accumulated data, mean systolic and diastolic blood pressures fell by 24+/-14 and 13+/-9 mm Hg (both P<0.001). The differences between the blood pressure-reducing effects of nebivolol monotherapy and add-on therapy were not statistically significant: 28+/-16 and 22+/-14 mm Hg for systolic and 15+/-11 and 11+/-8 mm Hg for diastolic blood pressures. Adverse events were limited to 0.5% of the patients, no serious adverse events were observed. In the ISH patients, diastolic blood pressure fell by 4+/-6 mm Hg compared with 15+/-10 mm Hg in the no-ISH patients (P<0.01). Efficacy-safety effects of nebivolol in patients with mild hypertension can be generalized in a nationwide assessment. The efficacy of nebivolol as monotherapy and as the efficacy as add-on therapy are very similar. Nebivolol is highly efficacious in patients with ISH.