Immunological function in patients with ovarian cancer was studied using parameters including peripheral blood lymphocyte counts, lymphocyte subsets, PHA-induced lymphoproliferative (PHA-LP) reaction, PPD skin test and immunoglobulin levels. The following results were obtained: The number of total lymphocytes, T cells (OKT 11+) and B cells (OKIa 1+) in peripheral blood were found to be decreased in patients with advanced carcinoma. The positive rate of PPD skin test was also lower in the patients. OKT8+ cells were significantly increased in the disseminated carcinoma (DC) group and the OKT4+/OKT8+ ratio in the DC group was markedly decreased when the results were compared with the control and the patients in the localized carcinoma (LC) group. PHA-LP reaction and serum IgM level in the patients in the LC and DC groups were found to be significantly lower than in the control group. The percentage of T cell (OKT11+), serum IgG and IgA levels were not altered in any clinical stage of the patients.