Since June 1978, 57 patients with primary osteogenic sarcoma of an extremity were treated with highdose methotrexate (HDMTX) and citrovorum factor rescue (CFR), Adriamycin, and the combination of bleomycin, cyclophosphamide and dactinomycin (BCD) given for 4-16 weeks prior to definitive surgery. Histologic examination of the resected primary tumor determined the effect of preoperative chemotherapy with many primary tumors showing greater than 90% tumor necrosis attributable to preoperative chemotherapy. A l l patients having this favorable effect of chemotherapy on the primary tumor were continued on the same chemotherapy regimen postoperatively (regimen B). However, in those patients not having a good effect of preoperative chemotherapy on the primary tumor, H D M T X with CFR was subsequently deleted from their postoperative chemotherapy and they were placed on a regimen containing cisplatinum at the dose of 120mg/M2 with mannitol diuresis combined with Adriamycin i n addition to BCD (regimen A). In the current study, 35 of the 57 patients did not demonstrate a good effect of chemotherapy on the primary tumor and were assigned to regimen A postoperatively. Of these 35 patients, 32 (91%)) have remained continuously free of recurrent or metastatic disease from 6-34 months following the start of therapy. Among the 22 remaining patients having a good histologic response and treated with regimen B postoperatively, there has been only one relapse in a patient who had a local recurrence in the area of an inadequately resected primary tumor three months after the cessation of chemotherapy. Thus, 53 of 57 patients (93%) are continuously with no evidence of recurrent or metastatic disease from 6-35 months (median, 20 months) from the start of treatment. This study demonstrates the value of thorough histologic examination in predicting survival i n responding patients and i n helping identify patients whose disease-free survival rate can be substantially increased if they are given alternative postoperative adjuvant chemotherapy after failing to have a good response to preoperative chemotherapy. This individualized chemotherapeutic strategy has yielded the highest disease-free survival raw reported to date for osteogenic sarcoma.