Increased morbidity and mortality from atherosclerotic vascular disease were observed in subjects with slightly elevated urinary albumin excretion rate (UAER), known as microalbuminuria. Therefore, the association between microalbuminuria and established atherogenic risk factors was studied in clinically healthy subjects. All healthy 40-65 year-old participants with microalbuminuria, examined within the first 21 months of The Copenhagen City Heart Study, were invited, and 28 were studied. An age- and sex-matched group of 60 randomly chosen subjects with normoalbuminuria served as control. Microalbuminuria was defined as a UAER of 6.6-150 micrograms/min, and normoalbuminuria as a UAER < or = 6.6 micrograms/min. In the microalbuminuric group, systolic and diastolic blood pressures were both elevated (mean (95% C.I.) 128 (123-134) vs. 119 (116-122) mmHg; P = 0.005, and 75 (71-78) vs. 69 (67-71) mmHg; P = 0.008, respectively), and serum apolipoprotein (apo) A-1 concentration was lower (1.30 (1.20-1.37) vs. 1.42 (1.36-1.47) milligrams; P = 0.02) in comparison with the normoalbuminuric group. Furthermore, serum HDL-cholesterol concentration tended to be lower, whereas body weight, body mass index and fasting serum insulin concentration were slightly elevated in the microalbuminuric group but not statistically significant. It is concluded that microalbuminuria in clinically healthy subjects is associated with increased levels of atherogenic risk factors. This may contribute to the increased vascular morbidity and mortality observed in these individuals.