Pretreatment assessment of blood lymphoid cells was performed in 44 patients with carcinoma of the cervix and in 19 healthy controls. White blood cells were determined by routine differential counting, and T-lymphocyte subsets and monocytes were quantitated using monoclonal antibodies. Increase in monocyte numbers, as determined by the 1D5 antibody, was seen in the cancer patients, especially in the group with advanced disease. No change in T-lymphocyte subpopulations could be found. During the 5-year follow-up period, 17 patients had a recurrence or died of cancer. The best prognostic information was obtained from conventional clinical parameters, e.g. stage, tumor size and lymph node status. Increased numbers of granulocytes and monocytes were found in advanced stage disease but had no independent prognostic influence. In pelvic lymph node biopsies taken from patients undergoing Wertheim-Meigs operation the T-helper/T-suppressor ratio was higher and the monocyte number lower than in peripheral blood. No correlation could be detected between node cell distribution and the prognosis. It is concluded that immunological testing, as performed in this study, elicits very little new prognostic information.