In the five kinds of human cultured cells derived from ovarian adenocarcinoma (HOC-21), ovarian malignant teratoma (HOTC 3), carcinoma of the uterine endometrium (HEC-1B), squamous cell carcinoma of the uterine cervix (SKG-1) and choriocarcinoma (BeWo), the intracellular presence of lactic dehydrogenase (LDH), alkaline phosphatase (AlP), human chorionic gonadotropin (HCG), alpha-fetoprotein (AFP) and plasminogen activator were investigated. The results were as follows. 1) BeWo-, HOC-21-and HOTC 3-cells revealed high activity of intracellular presence of lactic dehydrogenase (LDH), alkaline phosphatase (AlP), human chorionic gonadotropin (HCG), alpha-fetoprotein (AFP) and plasminogen activator were investigated. The results were as follows. 1) BeWo-, HOC-21-and HOTC 3-cells revealed high activity of intracellular LDH in this order, however none of HEC-1B-and SKG-1-cells did. 2) The activity of intracellular AlP was higher in BeWo-cells than in HOC-21-cells. The isozymes of AlP detected in these cells were found to be heat-stable. The others revealed no activity of AlP. 3) The presence of HCG-beta was confirmed in both BeWo- and HOTC 3-cells. The intracellular levels of HCG-beta were found to be higher in BeWo- cells than in HOTC 3-cells. HCG-beta was observed to leak into culture medium not from HOTC 3-cells but from BeWo-cells. It was not detected in the other cultured cells. 4) No AFP was detected in any of these five cultured cells. 5) Plasminogen activator was detected in HOC-21, HEC-1B-and SKG-1-cells in contrast to HOTC 3-and BeWo-cells which were negative for plasminogen activator. These results suggest that the various marker substances detected in the human cultured cells originated from various carcinomas of sexual organs may reflect biological functions of these tumor cells and, furthermore, can apply as tumor markers to the clinical diagnosis of the diseases.