The histochemical distribution of 14 enzymes in the human amnion at term are described. Adenosine triphosphatase, 5'-nucleotidase, acid phosphatase and nonspecific esterase show continuous gradations of enzyme activity. Cells with intense activity are prominent in acid phosphatase and nonspecific esterase preparations. A distinct subpopulation of amniotic cells can be defined by their alkaline phosphatase activity. The possible correlations with morphological studies are discussed.