Technetium-99m stannous pyrophosphate (Tc-PYP) cardiac scintiphotos were performed on 101 of 221 patients admitted to the Coronary Care Unit to rule out acute myocardial infarction (AMI). Criteria were defined for the diagnosis of AMI, variant angina and unstable angina. 42 patients were diagnosed as having had an AMI. 22 patients had transmural and 20 patients had nontransmural AMI. 40 of the 42 patients with AMI (95%) had positive scintiphotos; 2 (5%) had negative scintiphotos. 59 patients did not have an AMI; (97%) had negative scintiphotos. Four of these 59 patients had variant angina; all had negative scintiphotos. Seven of these 59 patients had unstable angina; 2 had positive scintiphotos. Tc-PYP scintiphotos have high sensitivity and specificity and are accurate in correctly classifying patients as having or not having AMI.