Cardiac troponin (cTn) assays were compared in 490 unselected patients with symptoms suggestive of acute coronary syndrome with varying renal functions for risk stratification. cTnI (Dade, Newark, NJ; Beckman, Chaska, MN; and Tosoh, South San Francisco, CA) and cTnT (Roche, Indianapolis, IN) measurements and estimated glomerular filtration rates (eGFRs) were obtained and classified along sex-derived cutoffs. The cTn levels were increased in 14% to 25% of patients. In 68%, the eGFR was 60 mL/min/1.73 m2 or more; in 17%, it was between 41 and 59; and in 15%, it was 40 or less. There were 36 deaths and 9 cardiac events. Risk stratification was significant at 30 days and 6 months (P < or = .05). Relative risks ranged from 3.1 to 3.7, and cumulative event rates ranged from 22.4% to 24.2% for an increased troponin level compared with 6.7% to 8.9% for a normal level. The 6-month event rate with an eGFR less than 60 mL/min/1.73 m2 and an increased troponin level ranged from 29.9% to 50.8% compared with 4.9% to 6.6% for a normal troponin level and an eGFR greater than 60 mL/min/1.73 m2 (P < .05). The eGFR in combination with an increased cTn level demonstrated the most powerful stratification.