Summary—In the present study an attempt was made to localize cytochemically ATPase activity in the epidermis ofPelobates syriacusduring its metamorphic cycle. In the epidermis of the legless tadpole, evidence for ATPase activity was confined intracellularly in two cell types: on the membranes of vesicles in the vesicle cells, and in the ER and Golgi inside the granular cell. This state continued throughout most of the tadpole life during the 2‐ and 4‐limbed stages. This is possibly an indication for either Ca2+‐ or Mg2+‐ATPases. Only in later stages, preceding metamorphic climax, did Na+‐K+‐ATPase activity shift to the baso‐lateral cell membranes bordering with the intercellular spaces. This continued after metamorphic climax in the juvenile toadlets, diminishing later in