Preliminary clinical trials using cryopreserved autologous bone marrow reinfusion have now been carried out at our institution in 5 children and 2 adults with advanced stages of neuroblastoma, rhabdomyosarcoma, non-Hodgkin's lymphoma and small cell carcinoma of the lung. Normal numbers of in vitro colony forming cells (CFU-C) were obtained from these patients despite prior courses of combination chemotherapy. The dose of marrow cells cryopreserved ranged from 1-6 X 10(8) cells/kg and recovery of CFU-C after thawing averaged 50%. Partial or complete hematologic reconstitution was achieved in all patients. The time for recovery ranged from 10-43 days for leukocytes (greater than 1000 cells/mm3) and 23-45 days for platelets (greater than 50,000/mm3). Two patients have died of interstitial pneumonitis due to cytomegalovirus. Three patients have died of recurrent tumor at 40, 48 and 156 days post-transplant. Two patients have had significant therapeutic benefit. One of these had a stable partial response permitting the use of further post-transplant therapy and is alive and well 16+ months post-transplant. The other patient had a complete response and remains tumor-free 25+ months following therapy. We conclude: 1) Autologous bone marrow reinfusion permits hematologic reconstitution following marrow-ablative therapy. 2) A quantity of marrow sufficient for this purpose remains viable following cryopreservation even when obtained from patients previously exposed to chemotherapy. 3) Autologous bone marrow reinfusion now allows the exploration of more intensive cytoreductive therapy in selected malignancies.