Twenty-five patients with metastatic carcinoma were entered into a Phase I clinical trial using poly(I,C)-LC at either 1 mg/m2 or 4 mg/m2 intravenous, twice weekly, for 4 weeks. None of the 15 patients entered at the 1 mg/m2 dose had an objective response; three had progressive disease. Similarly, no objective responses were observed among the 10 patients treated at the 4 mg/m2 dose of poly(I,C)-LC; one patient was removed from the study due to progressive disease. Toxicities observed at the 1 mg/m2 dose were mild hypotension, fever, nausea, vomiting, fatigue, and headache. The first patient treated at the 4 mg/m2 dose was taken off of the study for severe hypotension. In the subsequent nine patients treated at this dose, a pretreatment with one dose at 1 mg/m2 was given, and no further problems with hypotension were encountered. The other toxicities at 4 mg/m2 were similar to those seen at 1 mg/m2.