Oxalato-platinum in a new platinum derivative which was found to be active in experimental tumors and devoid of nephrotoxicity. A phase I study was conducted in cancer patients according to a new design following the recommendations of our Institution's ethical committee to avoid the major drawback of classical phase I studies in which many patients receive the experimental drug at doses far under the potentially active dose extrapolated from experimental studies. The potentially active dose of l-OHP was determined from the Maximally Efficient Dose Range (MEDR) to be between 45 mg/m2 (subcurative dose) and 67 mg/m2 (subtoxic dose). The patients in this study received with increasing intervals 1/100, 1/10, 1/5, 1/3, 1/2, 2/3, 3/4, 1, of the low dose of the MEDR, this dose being reached after 90 to 120 days on study. 23 evaluable patients have entered the trial of which 19 reached the low dose of MEDR (45 mg/m2). Gastro-intestinal toxicity, nausea and vomiting, similar to those with CDDP occurred in all patients at or above the dose of 30 mg/m2. Renal toxicity was monitored with creatinine level and did not occur in any patient at any dose nor did significant hematologic toxicity occur. Thus nausea and vomiting appear to be the limiting toxicity of the drug. Responses were observed in this phase I study in lung cancer (1), breast cancer (1), melanoma (1) and perhaps hepatoma (major decrease in alpha FP levels) (1). The proposed starting dose for phase II studies is 45 mg/m2 but we plan to continue dose escalation during the phase II according to the design of Jones and Holland. This new study design allows each patient entering a phase I study to be treated with a potentially active dose of the drug studied.