A novel approach to adoptive immunotherapy is described in this study. Of 13 patients with malignant effusions, nine were treated by intraperitoneal (IP) instillation of intracavitary lymphocytes (ICL), activated ex vivo by recombinant interleukin-2 (rIL-2, Cetus Co., Emeryville, CA) with escalating doses of IP rIL-2 and four by IP rIL-2 alone. ICL and rIL-2 were administered by repeated peritoneal punctures. Patients were divided into two groups: group I of six patients, who received activated ICL with low doses of IP rIL-2 (total dose not exceeding 6 X 10(5) units) and group II of seven patients, in whom escalating higher doses of rIL-2 were administered IP with or without activated ICL, in doses ranging from 10(6) up to 16 X 10(6) units, total dose. Total dose of ICL given ranged from 2 X 10(8) to 2 X 10(9) in both groups. The main objectives of this pilot study was to establish the feasibility of treatment by ex vivo activated ICL and IP rIL-2, to assess the toxicity associated with such a treatment, to escalate doses of rIL-2 to a maximal tolerable dose, and to look for clinical responses. The first two goals were achieved: such a treatment approach is feasible and is not associated with severe toxicity. The side effects observed during this study were usually mild in group I patients and more pronounced in group II patients. These included transient fever, chills, nausea, cellulitis at the puncture site, and one case of peritonitis.(ABSTRACT TRUNCATED AT 250 WORDS)