Preliminary observation on immunocytochemical localization of anti-HCG and anti-HPL in 49 patients with gestational trophoblastic neoplasms was studied. The findings were; (1) staining patterns to the two antibodies were different in cytotrophoblasts (CT), intermediate trophoblasts (IT), and syncytiotrophoblasts (ST) of the different types of trophoblastic tumor, (2)STs in tumors of all patients except one, showed positive staining of anti-HCG, and ITs in 17 cases of HM, 10 cases of IM and 1 case of GC were stained positively for anti-HCG; (3)STs in all of the 29 cases of HM, 14 cases of IM and 1 case of GC were positive for anti-HPL, ITs in 22 cases of HM, 11 cases of IM and 2 cases of GC were stained positively for anti-HPL. CTs in all tumors of the 49 patients were devoid of HCG and HPL. The results indicated that the production of HPL was found in well-differentiated cells and HCG in undifferentiated cells. The prognostic value of immunocytochemical localization of the two antibodies in trophoblastic tumors needs to be further clarified.