Background and Methods Cardiac troponin I (cTnl) is well recognized as a specific marker for myocardial infarction. A fully automated, random access, fluorescent immunoassay for cTnl was evaluated in comparison with an established assay (Stratus cTnl) using samples from healthy subjects and from patients with cardiac disease. Results The detection and precision were acceptable, and no interference was observed from bilirubin, triglycerides, haemoglobin, rheumatoid factor, drugs (aspirin, dopamine, digoxin) or heparin. Results on the Kryptor cTnl assay correlated with those on the Stratus 11 cTnl assay. The optimum Kryptor cTrl concentration for acute myocardial infarction was 0.63 mug/L, with a sensitivity of 89% [95% confidence interval (Cl): 75.9-96.3] and specificity of 98.9% (95% Cl: 93.9-99.8). Conclusion Kryptor cTnl immunoassay is suitable for use in the diagnosis of myocardial infarction.