We studied several ''in vitro'' activities of tumor-associated lymphomonocytes (TALM) and the levels of IL-1α, IL-1β, IL-2, IL-6, TNFα and soluble IL-2 receptor (sIL-2R) in neoplastic effusions and in the serum of advanced stage cancer patients. Comparisons were made with the behavior of autologous peripheral blood mononuclear cells (PBMC) using PBMC from normal subjects as controls. TALM were collected from 12 peritoneal and 15 pleural neoplastic effusions. The peritoneal effusions were mainly secondary to primary ovarian cancers and included 1 breast cancer as primary. The pleural effusions were secondary to primary lung and breast cancers. The blastic response to PHA and anti-CD3 monoclonal antibody (mAb) of TALM was lower than that of autologous PBMC, whereas proliferative response to recombinant IL-2 of both TALM and autologous PBMC was in the same range. Blastic responses of patient PBMC were lower than those of control PBMC. No significant differences were found for the expression of IL-2R subunities after PHA or anti-CD3 mAb stimulation between TALM and autologous PBMC, which, in both cases, was lower than that of control PBMC. After PHA stimulation, the levels of IL-1α, IL-1β and TNFα in culture media of TALM were lower than those of autologous PBMC, whereas, IL-2 and IL-6 levels were significantly higher. The cytokine production from patient PBMC was always lower than that of control PBMC. The levels of IL-6, TNFα and sIL-2R in neoplastic effusions were significantly higher than those of autologous serum. The levels of all cytokines were higher in patient than in control sera. Our data seem to suggest that a general impairment of the immune function is present in cancer patients with advanced disease, such as those with neoplastic effusions, involving not only TALM but also autologous PBMC.