Balb/c male mice infected i.p. with 2 x 10(5) plaque forming units (PFU) of coxsackievirus B3 (CVB3) develop severe myocarditis 7 days later. Studies were performed to determine whether therapy with normal polyclonal immunoglobulin would prevent cardiac inflammation. Partially purified immunoglobulin was derived from pooled mouse serum by ammonium sulphate precipitation. Infected animals given either 100 or 1000 micrograms of this preparation for 2 days prior to infection showed greater than 50% reduction in myocarditis compared to control animals which were infected and given either phosphate buffered saline, human immunoglobulin or monoclonal mouse IgG to an extraneous antigen. Protection did not depend upon inhibition of virus infection since cardiac viral titres were frequently equivalent in control and immunoglobulin-treated groups.