Distribution of alkaline β-glycerophosphatase in two young human embryos of 5 and 8 somites was observed histochemically. In most part of these specimens, the highest activity of the enzyme was detected in neural groove, neural crests, integumentary ectoderm, otic plate, cloacal membrane, gut endoderm and primordial germ cells. In the mesoderm and the notochord, gradated activity of the enzyme was noticed which diminished in its intensity in a caudo-cranial direction. Probable significance of such a gradient of the enzymic activity was also discussed in this report. Sections through the tail region, on the other hand, showed intense and even staining throughout ectodermic, mesodermic and endodermic layers. The epithelial cells of amnion, yolk sac and chorion revealed only a faint or moderate reaction in their free surface, while the mesodermic layer of these fetal membranes showed no remarkable activity of the enzyme.