Primary reactions on the addition of the epidermal growth factor (EGF) were investigated for the strains of A-431 cells, resistant to the antiproliferative effect of EGF. In spite of differences of EGF reception in the obtained strains, the EGF receptors in membrane preparations of these strains maintain the phosphorylating ability after addition of EGF. The rate of internalization of 125I-EGF in normal and resistant cells is the same. The production of a secreted fragment of the EGF receptor in resistant cells is lower than in normal ones. Questions of regulation of production of the normal receptor and of its shortened secreted fragment are discussed.