The relation between urinary albumin excretion rate (AER) and vascular disease was studied in 187 subjects aged over 40 selected from 1084 cases attending a diabetic screening project. AER exceeded 20 micrograms/min in 3 of 13 newly diagnosed diabetic subjects (23%) and 16 of 171 non-diabetic subjects (9.4%). There was a weak relation between AER and both systolic and diastolic blood pressures. Coronary heart disease was found in 54 of 164 (32.9%) subjects with AER of 20 micrograms/min or less and in 14 of 19 (74%) with AER above this. Peripheral vascular disease was present in 16 of 165 (9.7%) subjects with AER of 20 micrograms/min or less and 8 of 18 (44%) with a high AER. Logistic regression, including diabetes, impaired glucose tolerance, systolic and diastolic blood pressures, smoking, age, sex, ethnic origin, and body mass index, demonstrated the independence of this relation between AER above 20 micrograms/min and coronary heart disease (odds ratio [OR] 6.38, 95% confidence interval 1.91-21.4) and peripheral vascular disease (OR 7.72, 2.14-27.8). After a mean of 3.6 (SD 0.19) years, 167 subjects (89.3%) were traced. There had been 9 deaths, 3 (2.0%) among 149 subjects with normal AER and 6 (33%) among 18 microalbuminuric subjects (OR 24.33, 5.40-109.7).