Serum histaminase and SGOT were estimated in 35 cases of acute myocardial infarction and 34 cases of ischaemic heart disease (Other than acute myocardial infarction) and 30, age and sex match-ed, healthy subjects which served as controls, to evaluate the com-parison of time relation activity, diagnostic and prognostic value of histaminase and SGOT. The enzymes were estimated within 6 hours, then repeated -within 24 hours, 2nd day, 3rd day, 5th day, 10th day and 15th day, ascertained from the time o f pain in the chest. Raised histaminase levels were found in 97.14%; cases, while SGOT levels were found elevated in only 91.4% cases of acute myo-cardial infarction of which 30 were electrocardiographically proved and 5 had equivocal electrocardiographic evidence of acute infarc-tion like LBBB, complete heart block, ventricular tachycardia and old myocardial infarction. Furthermore elevation of histaminase was 6.2 times whereas of SGOT only 5.2 times above the mean normal value. Serum histaminase was found elevated in all the 6 cases who presented within 6 hours of infarction, while SGOT did not rise in any of these cases. Both histaminase and SGOT reached the peak levels on the 2nd day and persisted for whole of the first week. Higher levels of these enzymes were found associated with worse prognosis. Above observations show that the serum histaminase rises earlier than SGOT and can prove the diagnosis of myocardial infarction even when SGOT and ECG fail to reveal the diagnosis. It is a more sensitive index and has higher peak rise of levels than SGOT. How-ever its pattern of rise, fall and prognostic values are similar to that of SGOT