50 cases of acute myocardial infarction (AMI) were examined for ventricular late potential (VLP) six times in total within 4 weeks. At the same time the patients clinical condition was observed. It is found that: (1) In our group the occurrence of VLP in AMI was 28% and VLP was unstable in both acute stage and recovery stage. (2) During acute stage, the difference of positive VLP rate is significant between the ventricular fibrillation group and normal rhythm group (P less than 0.05), but there is no significant difference between the ventricular ectopia group and normal rhythm group. During recovery stage, the difference of positive VLP rate is very significant between the ventricular ectopia and normal rhythm group (P = 0.001). As there was only 1 case of ventricular fibrillation occurring in the recovery stage, no comparison could be made. (3) There is no correlation between VLP and clinical conditions, such as age sex, location of the infarction, existence of old infarction and LVEF. However, the difference of the peak serum CPK level is significant between VLP positive and negative group (P less than 0.05).