A phase I trial of cisplatin in hypertonic saline and escalating doses of 5-fluorouracil by continuous intravenous infusion in patients with advanced malignancies. Thirty-four patients with incurable solid tumors were treated in a Phase I trial with a fixed dose of high-dose cisplatin (CDDP) administered in hypertonic saline and escalating doses of infusional 5-fluorouracil (5-FU). Five treatment levels of 5-FU, ranging from 500 to 900 mg/m2/day for 5 days, were studied. Leukopenia, thrombocytopenia, and oral mucositis were the dose-limiting toxicities encountered. Nephrotoxicity was minimal. Ototoxicity and peripheral neuropathies were rare and mild in this patient group, but most patients received only a small number of treatment cycles. Diarrhea was not dose-limiting. Two complete responses (one non-small cell lung cancer and one sweat gland carcinoma) were observed. No other major responses were noted. With the dose of CDDP set at 35 mg/m2/day for 5 consecutive days, the maximum tolerated dose (MTD) of a concurrent 5-day 5-FU infusion was found to be 900 mg/m2/day. The recommended dosages for Phase II trials are 35 mg/m2/day CDDP and 800 mg/m2/day 5-FU for 5 consecutive days. Cancers of the lung, breast, gastrointestinal tract, and genitourinary tract would be reasonable targets for Phase II studies. 