The value of adjuvant chemotherapy in primary osteogenic sarcoma (OSA) is still considered controversial by some. One reason may be that various reported series include patients with widely varying prognostic variables. To address this, the effect of chemotherapy on the continuous disease-free (CNED) survival was analyzed in 100 patients aged 21 yr or less with OSA of the femur. This classically poor prognostic group of patients represented 51% of all primary OSA seen at the Memorial Sloan-Kettering Cancer Center during the study interval. This study includes all patients aged 21 yr or less with fully malignant (Grade III-IV/IV) OSA of the femur and no metastases treated from November 1973 through November 1981. The first (T-4) protocol (31 patients) consisted of high dose methotrexate (HDMTX) with leucovorin rescue, cyclophosphamide (Cyc), and adriamycin. In the second (T-7) protocol (23 patients) the dose of HDMTX was increased to 12 g/m2 for prepubescent patients, and bleomycin, Cyc, and dactinomycin replaced Cyc. The current (T-10) protocol (46 patients) uses the same CT as T-7, but patients not having a complete response of the primary tumor to preoperative CT receive additional cisplatinum (120 mg/m2) with adriamycin (30 mg/m2/day for two consecutive days). In 31 patients treated with T-4 the CNED survival was 32% with a minimum follow up of over 7 yr. On T-7, 15/23 patients with femur primaries had a CNED survival of 65% with all of the surviving patients followed for more than 5 yr. The addition of cisplatinum in T-10 has resulted in CNED survival rate of 77% in 34/44 patients (excluding two patients that died CNED during and after treatment); the median follow-up patients who are alive CNED is 33 months, with a minimum of 2 yr follow up on the last patient entered.