A study was carried out on the plasma levels of 6 Keto PGF1 alpha and Thromboxane B2 (TXB2) in patients with acute myocardial infarction. Our results showed a generalized increase in the levels after acute myocardial infarction. The 6 Keto PGF1 alpha levels increased twice as compared to control values while the TXB2 levels increased nine times as compared to control values. The prostaglandin levels were found to increase from day 1 to day 3 and further from day 3 to day 7. In most of the patients with uncomplicated myocardial infarction the 6 Keto PGF1 alpha levels were higher than the TXB2 levels. In patients with myocardial infarction accompanied by arrhythmias the TXB2 levels dominated over the 6 Keto PGF1 alpha levels.