Dinitrophenol (DNP), an inhibitor of endocytosis of hormone receptors, Tris, an inhibitor of recycling and chloroquine, an inhibitor of lysosomal degradation, all decreased the binding of insulin and inhibited the development of hormonal imprinting in Tetrahymena. The effects of DNP and Tris seemed to be similar even quantitatively. The effect of chloroquine proved to be somewhat different, it appeared later, was more pronounced after 24 hours and more marked when insulin was also administered. Combined administration of Tris + DNP inhibited the binding of insulin but this inhibition was the one which disappeared most completely after 24 hours and the one where the inhibition of imprinting was the most pronounced. Tris + chloroquine led to severe destruction of the cells. The conclusion has been drawn that the inhibition of membrane circulation inhibits not only the hormone binding but also the development of imprinting in Tetrahymena.