A generation of lymphokine-activated killer (LAK) cell activities from malignant peritoneal effusions was investigated in 10 patients with abdominal carcinomatosis. Five of the 10 patients were victims of colorectal cancers, three of gastric cancers, and one each of ovarian cancer and cholangiocarcinoma. Lymphocytes, the so-called effusion associated lymphocytes (EALs), were isolated from malignant peritoneal effusions by density gradient centrifugation and the plastic adherence method. These isolated EALs were subsequently cultured in the presence of recombinant interleukin-2(rIL-2), 3,000 I.U./ml, for 30 days. Natural killer (NK) cell activities and LAK cell activities of the freshly isolated and cultured EALs were examined at 0, 7, 14, and 30 days of culture by means of a standard 51Cr-release assay using K-562, HL-60, and autologous tumor cells as target cells. The NK cell activities of the freshly isolated EALs were not detected in any of the 10 patients. The LAK activities, however, could be generated in all of them, and the activities were maximal at 7 days. The longer the EALs remained in the culture, the weaker were the LAK cell activities. As far as cell growth was concerned, EALs proliferated well as long as the rIL-2 were present in the culture. Phenotypic analysis of the freshly isolated EALs revealed the presence of NK cells (22%, CD16+CD56+), T helper/inducer (18%, CD4+), T cytotoxic/suppressor (50%, CD8+), and B cells (8%, CD19+). After being cultured with rIL-2, the B lymphocytes gradually disappeared, and the T lymphocytes predominated with an increase in the percentage of T helper/inducer cells.(ABSTRACT TRUNCATED AT 250 WORDS)