The authors studied histologically six of 35 massive osseous or osteochondral transplants that had been inserted following radical resection of musculoskeletal malignancies. The six transplants consisted of three allografts removed because of infection within 12 weeks following insertion and two allografts and one vascularized autograft resected between 52 and 72 weeks because of recurrent tumor. The infected allografts were necrotic and showed extensive osteomyelitis and septic arthritis. Focal areas of cartilage still had chondrocytes. The two non-infected allografts were also necrotic, and host bone had grown into donor bone at the graft--host interface. The vascularized autograft was viable. Articular cartilage was present in only one of the non-infected allografts and was necrotic. Ultrastructurally, allograft cartilage, although necrotic, showed marked destruction of the matrix only when infected. Allograft bone seems to act purely as a strut, inciting little immune response. It is unable to respond to infection and has little osteoinductive ability. Vascularized autograft, in contrast, appeared to contribute to graft union. Articular cartilage can survive transplantation but may become necrotic and undergo marked degeneration when infected. The histologic findings and clinical courses support the conclusion that graft failure within 72 weeks after transplantation is not due to immunologic rejection.