The human epidermal growth factor receptor (hEGF-R) was introduced into murine P19 embryonal carcinoma (EC) cells, which do not express endogenous EGF-R. Undifferentiated stable P19 EC transfectants containing multiple copies of the hEGF-R complementary DNA were isolated. These cells express functional EGF-R, exhibiting characteristic biphasic EGF binding and intrinsic tyrosine protein kinase activity. Whereas normally EGF induces the expression of multiple nuclear protooncogenes, only junB expression is induced by EGF in the HER-transfected cells. This indicates that undifferentiated P19 EC cells contain at least part of a signal transduction machinery capable of coupling to the ectopically expressed hEGF-R. Interestingly, neuronal differentiation is induced in these cells in response to EGF under culture conditions resembling those during early preimplantation embryogenesis. These results indicate that neuronal differentiation of pluripotent P19 EC cells can be induced via activation of a tyrosine protein kinase signaling pathway.