Hypersensitivity myocarditis is a rare event; however, routine histologic examination of all (193) explanted hearts for heart transplantation in our institutions revealed hypersensitivity myocarditis in 15 patients (7%). This is a previously unreported finding in heart transplant recipients. None of the cases was detected clinically, although all manifested peripheral eosinophilia at some point during the 2 weeks before transplantation. Only one patient exhibited a skin rash interpreted as allergic. The severity of the interstitial infiltrate varied from grade I to grade IV (semiquantitative). This group of pretransplantation patients was receiving a multiplicity of drugs, some of which could have potentially triggered the hypersensitivity myocarditis, although in only one case was a definite association between a hypersensitivity reaction and a drug made. The unusually high rate (10.3% for the Emory cases) of drug-induced myocarditis in this group of patients, contrasted with the general autopsy population, probably reflects that these patients received more vigorous than usual drug treatment, particularly antibiotics, to sustain them until a suitable donor was found.