The PAG (Pregnancy-Associated Glycoproteins) gene family and chorionic expressions of their products suggest an important role(s) of this glycoprotein family throughout pregnancy in various mammals (pig, cattle, sheep, goat, hourse, zebra, cat and mouse). Each cloned cDNA is a major source of template for recombinant PAG protein productions, necessitated for requirements at various diagnostic tests of early pregnancy in ruminants. Moreover, each cDNA may be applied as template for preparation of selective genetic tests (i.e. micro-arrays), can provide essential background for estimation of correlations between various PAG genotypes and physiological reproductivity of each animal. Aforementioned genetic tests presumably will allow for pre-selection of young indyviduals with effective reproductive performances.