Crude gonadotropins extracted from the urine of patients with chorioepithelioma (choriocarcinoma) by Bradbury method was purified by a combination of Sephadex gel filtration, CM-C and DEAE-C chromatography. Two biologically active fractions (fraction t-hCG-A and fraction t-hCG-C) were obtained. The former cross-reacted with anti-hCG sera and the latter cross-reacted with anti-hCFSH sera in experiments with Ouchterlony immunodiffusion and immunoelectrophoresis. But the hCG or hCFSH from normal pregnancy and t-hCG-C from choriocarcinoma were different in their potency of being adsorbed on ion-exchange cellulose respectively. T-hCG-C was poorer in aspartic acid and glycine, and richer in serine, threonine and tyrosin to which carbohydrates bind than hCFSH from normal pregnancy. These two fractions contained high concentrations of carbohydrates, especially hexose and sialic acid, less concentration of hexosamine, compared to those of hCG and hCFSH obtained from urine of normal pregnant women. Sera of normal pregnant women in the first and third trimester and those of patients with chorionic neoplasias were gel filtrated on a Sephadex G-100 upward flow column in the same conditions. Biological activity of hCG in sera of normal pregnant women was recognized in 2-3 peaks on the gel filtration, and the molecular weights of those were considered to be about 25,000-40,000. In case of sera of chorionic neoplasias, however, it was admitted as multi-peaks (the molecular weights: about 10,000-70,000). It might be one of the features of chorionic neoplasias that the biological activity was found even in fractions of molecular weight 10,000 on the gel filtration, and to pay attention to this phenomenon might be a useful sign for the diagnosis or the management of patients with chorionic neoplasias. As a conclusion, all the above findings suggest that the molecular structure of t-hCG-A and t-hCG-C from choriocarcinoma differes from that of hCG and hCFSH from normal pregnancy respectively.