Objective To develop a method for measuring creatine kinase MB (CK-MB) isoforms which is rapid for clinical diagnosis of acute myocardial infarction.Methods A simple agarose gel electrophoresis was developed for CK isoforms. A suitable discontinuous buffer system separated CK-MB and CK-MM isoforms simultaneously in 30 minutes under low voltage. The results were obtained in 1 hour. 45 patients with AMI were divided into two groups: conventionally treated group (n=38) and reperfusion group (n=7). Three control groups were also studied: apparently healthy volunteers (n=40),unstable angina patients (n=30) and hospitalized adult patients with no history of myocardial ischemia (n=25).Results In 45 patients with AMI and 95 patients without AMI, we found that the ratio of MB2 to MB1 was a high sensitive index for early diagnosis of AMI. The sensitivity was 62% in the first 2 hours after onset of chest pain, 92% in 2-4 hours, and 97% in 8-12 hours.Conclusion CK-MB isoforms can be used for early diagnosis of AMI. Agarose electrophoresis is widely used in clinical laboratory.