BACKGROUND One-third of patients with rest angina are reported to have detectable cardiac troponin T in the serum and may be at increased risk of serious cardiac events. OBJECTIVE To investigate whether a single early estimation of serum troponin T was an independent predictor of serious cardiovascular complications in patients with suspected unstable angina. METHODS A prospective cohort study in which patients with suspected rest angina had a serum troponin T estimation 14 hours after symptom onset and were classified using discriminator levels of serum troponin T of 0.05 and 0.1 microgram/L as well as a number of other variables. All patients were followed for six months to document any cardiac complications and a stepwise logistic regression analysis was conducted to determine independent risk factors of complications. RESULTS One hundred and sixty-four patients were evaluated. Using a discriminator level of 0.05 microgram/L 54 patients (33%) had detectable troponin T. The admission ECG was the only independent predictor of cardiac events in hospital--odds ratio 4.0 (95% CI 1.7-9.6). Detectable troponin T did not appear to be an independent predictor of serious complications. During the six-month follow-up period, detectable troponin T using a discriminator of 0.05 microgram/L was an independent predictor of serious complications--odds ratio 3.7 (95% CI 1.8-7.6). CONCLUSIONS In patients with suspected rest angina, detectable serum troponin T > 0.05 microgram/L is an independent predictor of serious cardiac events during the six-month follow-up period although not during hospitalisation. Using a single, early serum troponin T estimation and other variables available at the time of admission, a high risk subgroup who may benefit from early investigation and revascularisation can be identified.