Abstract Coxsackievirus B-3 myocardiopathy was induced in weanling mice by intraperitoneal and intracerebral inoculations of the Nancy strain. Acute mortality was 5.5%. The cardiomyopathy is characterized by an early phase lasting about 9 days with myocardial necrosis, associated inflammation, and healing by fibrosis and calcification involving 25 to 50% of the contractile fibers in each affected mouse. Infectious coxsackievirus may be recovered from the heart during this phase.