Cutaneous lesions develop frequently in patients infected with human immunodeficiency virus (HIV). We describe the clinical features of four patients with the acquired immunodeficiency syndrome (AIDS) or AIDS-related complex who developed angiomatous nodules involving skin and bone, 2 of whom were scratched by a cat. Some of these lesions were clinically indistinguishable from Kaposi sarcoma. When examined with Warthin-Starry staining and electronmicroscopy, these nodules were noted to contain numerous clumps of a bacterium. Immunoperoxidase staining with an antiserum raised against the cat-scratch disease bacillus stained these organisms in all patients. Cat-scratch disease is usually a self-limited infection, but complicated or prolonged infections have been described in both normal and immunocompromised hosts. In our patients infected with HIV, manifestations of systemic cat-scratch disease included angiomatous nodules, severe systemic symptoms of fever, chills, night sweats and weight loss, elevated erythrocyte sedimentation rate, and decreased hematocrit. Cutaneous lesions involved the face, trunk, and extremities and numbered 2 to greater than 60; osseous lesions involved the fibula, radius, femur, and tibia, and were present in two of four patients. Treatment with x-ray therapy, intralesional vinblastine, penicillin, dicloxacillin, cephradine, and nafcillin had no effect on any lesions; however, treatment with erythromycin, doxycyline, or antimycobacterial antibiotics resulted in complete and rapid resolution of the cutaneous and osseous lesions, and the accompanying signs and symptoms of systemic infection. In patients with AIDS or AIDS-related complex, angiomatous nodules should be carefully evaluated for the presence of this organism, which can be treated and cured with antibiotic agents.