Objective: To investigate inhibitory effect of recombinant TGFα-PE40 (TP40) on cultured vascular smooth muscle cells (SMC). Methods: Expression of epidermal growth factor receptor (EGFR) in SMC was analysed with immunohistochemistry. Inhibitory effects of TP40 on SMC proliferation and protein synthesis were analysed by crystal violet staining and 3H-leucine incorporation. Competition assays were performed by the addition of excess of EGF. Results: Expression of EGFR was found in rapidly proliferating SMC, not found in quiescent SMC. Inhibitory effects of TP40 on rapidly proliferating SMC proliferation and protein synthsis was much higher than on quiescent SMC. Excess EGF can completely block inhibitory effects of TP40. Conclusion: It indicates that TP40 can significantly inhibit the proliferation of rapidly proliferating SMC, but less confluence quiescent SMC. The cytotoxic effects of TP40 are specifically mediaed by EGFR.