cis-Platinum (DDP) and cyclophosphamide are commonly used for the treatment of ovarian cancer; however, survival remains poor. The degree of cytotoxicity of the standard antineoplastic agents DDP, 4-hydroperoxy-cyclophosphamide (4-OH-CTX), mitomycin C (MITOM C), vincristine (VCR), etoposide (VP-16), 5-fluorouracil (5-FU), cytosine arabinoside (ARA-C), and interferon (IF) in four representative ovarian cancer cell lines was studied using the ATP assay, which measures total cell kill. Cell lines CAOV-3, OVCAR-3, SKOV-3, and BG-1, which were derived from both pretreated and untreated patients, were exposed to six different concentrations for 90 min. On Day 7, intracellular ATP determinations were done. Sensitivity was defined as greater than or equal to 50% cell kill at 0.5 x peak plasma concentration as compared to controls. For 4-OH-CTX and ARA-C, 3 and 0.5 micrograms/ml were chosen as 0.5 x reference values. For each drug in each cell line, a highly reproducible dose-response relationship was observed. CAOV-3 cells were sensitive to all drugs except DDP, ARA-C, and IF, and OVCAR-3 cells to all except DDP and IF. SKOV-3 cells were resistant to all agents except VCR, and BG-1 cells to all except MITOM C and 5-FU. The apparent heterogeneic response to antineoplastic agents observed in the above cell lines underscores the importance of assessing individual patients' sensitivity profiles before treatment.