The aim of this study was to investigate the predictive value of microalbuminuria (overnight urinary albumin excretion rate 17 to 100 mg/12 h) as a risk factor for future major cardiovascular events in nondiabetic patients with treated hypertension in a prospective study with follow-up time of 3.3 years. Overnight urinary albumin excretion was measured in 345 nondiabetic treated hypertensive men, aged 50 to 72 years, either with a serum cholesterol of > or = 6.5 mmol/L or smokers, or both. Cardiovascular morbidity was closely recorded during the follow-up period. At entry, microalbuminuria was found in 84 patients (24.3%) and 12 patients had macroalbuminuria (3.5%). During the follow-up period there were no differences in new cardiovascular events between patients with microalbuminuria and those with normoalbuminuria. However, an increase in the risk of future major cardiovascular events occurred in patients with urinary albumin excretion above 100 mg/12 h (macroalbuminuria). In a Cox regression analysis urinary albumin excretion was not associated with the incidence of future major cardiovascular events unless a more detailed approach was used, showing that this was the case for urinary albumin excretion above 100 mg/12 h (macroalbuminuria). Calculations with an alternative definition of microalbuminuria and mortality as end-point did not change the principal result. In conclusion, microalbuminuria does not seem to be a predictor of future mortality and cardiovascular morbidity in nondiabetic men with treated hypertension and at high risk of coronary heart disease. However, macroalbuminuria was associated with future major cardiovascular events in this group of patients.