A clinical study was designed to evaluate the tolerance of cancer patients to liposome-associated doxorubicin (L-DXR). The liposomes used contain phosphatidylglycerol, phosphatidylcholine, cholesterol, and DXR intercalated in the lipid bilayer, and have a mean size in the range of 0.3-0.5 microns. Thirty-two patients, most of them with primary or metastatic liver cancer refractory to conventional therapy, were entered into the study. A total of 69 courses of therapy was administered by intravenous infusion of a suspension of L-DXR (0.5-2.0 mg DXR/ml) in physiologic saline at an approximate rate of 2 ml/min given on a 3-week intermittent schedule. The L-DXR and phospholipid doses were escalated from 20 mg/m2 and 0.3 g/m2 to 120 mg/m2 and 3.2 g/m2 respectively. Treatment was generally well tolerated and acute toxic effects such as nausea and vomiting were mild and infrequent. Chills and fever (greater than 38.0 degrees C) were observed in three patients during infusion of L-DXR and in seven patients 6-12 h after the end of infusion. Median WBC nadir counts were 2700, 2300 and 700/microliters at 85, 100 and 120 mg/m2 respectively. All three patients receiving 120 mg/m2 developed grade 4 leukopenia and fever requiring intravenous antibiotics, and, in two of them, severe stomatitis (grades 3 and 4) was observed. Significant hair loss was apparent in all patients receiving doses higher than 50 mg/m2. The maximal tolerated dose of L-DXR appears to be 120 mg/m2, with leukopenia and stomatitis being the dose-limiting factors. While the subacute toxicity of L-DXR appears to be qualitatively similar to that of free DXR, its tolerance exceeds the recommended dose of free DXR (75 mg/m2) in the standard 3-weekly schedule.