Cytomegalovirus (CMV)-associated carditis in the immunosuppressed patient carries a 60% mortality. Underlying pathogenesis is poorly understood but may involve either direct viral invasion or autoimmune cardiac damage triggered in response to the infection. Specific anti-cytomegalovirus therapy and/or anti-inflammatory drugs have been shown to benefit in cases where an early diagnosis was established. We report an unusual case of endo-pericarditis which was temporally related to acute cytomegalovirus infection diagnosed by the immediate early antigen detection in cell culture on whole blood.