Electrophoretic patterns of alkaline phosphatase and its activities at 20 developmental stages from cleavage to completion of metamorphosis and in 18 organs and plasma of adults were compared with one another in Rana japonica and Rana nigromaculata. The bands of alkaline phosphatase first appeared at the tail-bud stage in Rana japonica, while they appeared at the hatching tadpole stage in Rana nigromaculata. In each species, a distinct change in electrophoretic pattern occurred at an early tadpole stage, then at a late tadpole stage, and finally at the stage of complete metamorphosis. Ten kinds of isozymes of alkaline phosphatase were found in nine organs of Rana japonica, while seven kinds of isozymes were observed in eight organs and plasma of adult Rana nigromaculata.