As part of the observations on incubated eggs injected with P32 combined as KH2PO4, the course of the isotope was traced within the components of the egg throughout incubation. P32 was injected in the yolk on the 5th day of incubation The distribution of P32 within the various components of the eggs was detd. daily throughout incubation. There was an early shift of P32 from yolk to allantoic and amniotic fluid. The embryo''s content of P32 increased nearly in proportion to its gain in wt. and contained 90% of P32 at hatching. Albumen and shell did not contain significant amts. of activity at any time.