Twenty-five patients with advanced measurable gastric carcinoma were treated with D,L-leucovorin (CF) (500 mg/m2) administered as a 2-hour infusion and FUra (600 mg/m2) iv push midinfusion. Patients were treated weekly for 6 weeks followed by a 2-week rest. Median age was 57 (range 32 to 82). Median Eastern Cooperative Oncology Group (ECOG) performance status was 2 (range 0 to 4). Thirteen patients had progressed on previous combination chemotherapy that included FUra. At the time of this report, 19 patients were evaluable for response: 3 patients had partial responses, 8 had stable disease, and 8 progressed (but 3 of these received only 3 or fewer treatments before early disease-related death). Two of the responders were previously treated with FUra. Four patients were too early to evaluate. Measurable responses of greater than 50% were seen in bone, liver, lung, and an abdominal mass. Diarrhea occurred in 9 patients and FUra dose reduction was necessary in 8 of them. Other toxicities included lacrimation, rash, nausea, and mucositis. One toxic death occurred. Nine patients with gastrointestinal tumors confined primarily to the intra-abdominal space were treated with ip FUra in escalating doses (2 mM to 4 mM) in combination with D,L-CF in a 2-liter volume, either by 8 consecutive 4-hour dwells (7 patients) or once daily for 5 days (2 patients). The D,L-CF dose was 20.8 microM except for the first day of the 5-day schedule when it was 104 microM. Toxicity included leukopenia, mucositis, nausea and vomiting, skin rash, and abdominal pain. Three episodes of peritonitis resolved with antibiotics.(ABSTRACT TRUNCATED AT 250 WORDS)