Increased plasma levels of beta-thromboglobulin, a platelet activation marker, are observed in coronary artery disease. Urinary albumin excretion, a marker of endothelial cell perturbation, is related to cardiovascular disease in diabetes. To test the value of these markers in predicting forthcoming coronary disease, the relations between urinary excretions of high molecular weight beta-thromboglobulin (HMW-beta TGf) and albumin and subsequent coronary disease in a cohort of 15,484 middle-aged women were investigated in a nested case-control study. Baseline questionnaire data and urine samples were available from a breast cancer screening program in Utrecht during 1982-1985. Cases were Utrecht hospital admissions for myocardial infarction (n = 50) or angiographically confirmed coronary disease (n = 28) from 1982-1985 to 1990-1991. Classifying events occurred a median of 5.1 years after baseline. Controls were a random sample from the cohort, individually case matched for baseline examination date and age, at a 1:2 ratio. HMW-beta TG/creatinine ratios (ng/mmol, mean +/- standard error) were 5.3 +/- 0.3 in cases and 4.7 +/- 0.3 in controls; albumin/creatinine ratios (mg/mmol, median) were, respectively, 0.37 and 0.22. Crude odds ratios for classification in the highest compared with the lowest tertiles of HMW-beta TG/creatinine and albumin/creatinine distributions were elevated for cases compared with controls: HMW-beta TG/creatinine odds ratio = 2.4, 95% confidence interval 1.1-5.0; albumin/creatinine odds ratio = 2.1, 95% confidence interval 1.0-4.1. These relations persisted after adjustment for smoking, hypertension, Quetelet index, and menopausal status. Both urinary HMW-beta TG and albumin excretion are markers of coronary disease risk in middle-aged women, indicating that increased platelet activation and endothelial cell perturbation precede coronary heart disease events in women.