The alpha and beta subunits of the human chorionic gonadotropin (HCG) were measured during pregnancy in the saliva of a first group (no. = 23) and in the serum and saliva of a second group (no. = 25). Only ten pregnant women had normal gestation, the remaining 39 being diagnosed as miscellaneous pathologies, the threatened (or impending) abortion being the most frequent (no. = 19). The mean serum levels of alpha-HCG increase from 75.97 +/- 18.59 ng/ml (X +/- SEM) during the first trimester to 341.98 +/- 65.09 ng/ml during the third trimester of the gestation. The mean salivary concentration of the alpha HCG seems unmodified during pregnancy (approximately 10 ng/ml), but large interindividual variations were observed (limits 0.10-28.78 ng/ml) possibly due to the non-homogeneity of the investigated groups. The presence of the beta-HCG subunit in saliva could not be assessed, the great part of the values being aggregated around the sensitivity limit of the RIA technique (0.2 ng/ml). The physiological significance of the presence of the HCG and of its subunits in saliva as well as the ways to elucidate the possible selective role of the blood-saliva barrier are discussed.