The most common manifestations of the acquired immunodeficiency syndrome include Pneumocystis carinii pneumonia and/or Kaposi's sarcoma. High-grade B-cell lymphomas have also been reported in homosexual men at risk for the acquired immunodeficiency syndrome. We herein present the case of a homosexual man, who presented simultaneously with Pneumocystis carinii pneumonia, acute cytomegalovirus infection, Kaposi's sarcoma, and B-cell immunoblastic sarcoma. Severe compromise of both the B- and T-cell arms of the immune system was documented. The patient had evidence of exposure to the human T-lymphotropic retrovirus III, evidence of reactivation of Epstein-Barr virus infection, and cytomegalovirus inclusions within Kaposi's sarcoma tissue. We conclude that exposure to these viral agents in the setting of severe immunocompromise may have led to the observed "opportunistic" neoplasms.