It is a well known that cardiac arrest can occur during general anesthesia. We had experienced of a cardiac arrest during anesthsia in a child with halothane just after the use of a thiopental sodium and vecuronium bromide. When the cardiac asystole was noted by E.C.G., immediate treatment was performed. In this case, We think that Cardiac arrest being related to several factors, anxiety about operation, rough sugical maniplation, light anesthesia and drugs.