Although the T-cell receptor for antigen (TCR) lacks intrinsic kinase activity, stimulation of this receptor induces tyrosine phosphorylation of multiple substrates. In contrast, the epidermal growth factor receptor (EGFR) has intrinsic cytoplasmic tyrosine kinase catalytic activity that is activated upon EGF binding. To compare the functional effects of the TCR and a transmembrane protein tyrosine kinase (PTK), we used retrovirus-mediated gene transduction to express the human c-erbB proto-oncogene, encoding the EGFR, in a murine T-cell hybridoma. Tyrosine phosphorylation induced by the TCR and the EGFR occurred on substrates unique to each receptor as well as on several shared substrates, including the zeta chain of the TCR. Stimulation of the EGFR induced calcium ion flux in these cells, suggesting that the heterologous tyrosine kinase can couple to the T-cell phospholipase signal transduction pathway, but this stimulus did not lead to interleukin 2 production. However, EGF stimulation of transduced cells significantly enhanced TCR signaling, as assessed by interleukin 2 production, indicating that cross talk can occur between the TCR and a transmembrane PTK.