This paper describes the epidemiological and pathological features of an outbreak of clostridial myocarditis in calves due to Clostridium chauvoei. Four of seven two-month-old Hereford calves died in the course of a week. Their gross postmortem lesions were similar and consisted of irregular dark red areas of myocardial necrosis through the full thickness of the atrial and ventricular myocardium. No lesions were observed in skeletal muscle. The heart muscle had extensive multifocal areas of acute coagulative necrosis. The diagnosis was confirmed by a fluorescent antibody technique on tissue smears, by a streptavidin-biotin technique on formalin-fixed, paraffin-embedded tissues, and by a PCR technique specific for the 16S rRNA of C chauvoei.