Characteristics of specific receptors for epidermal growth factor (EGF) and its effect on cellular proliferation and synthesis of DNA and protein were studied in cultured vascular smooth muscle cells (VSMC) from rat aorta. Binding studies using 125I-EGF revealed the presence of high affinity binding sites for EGF on VSMC in culture: the apparent dissociation constant was approximately 2.5 X 10(-10)M and the maximal binding capacity was approximately 67,000 sites/cell. EGF stimulated cellular proliferation and incorporation of [3H]thymidine and [3H]leucine into the cells in a dose-dependent fashion; the approximate half-maximal stimulation was induced with 1.5 X 10(-10)M. Platelet-derived growth factor (PDGF) had an additive effect with EGF on DNA synthesis by VSMC. Preincubation of VSMC with unlabeled EGF resulted in a substantial reduction in the number of receptors without changing the affinity, suggesting receptor "down-regulation" mechanism. These data indicate that rat aortic VSMCs have specific receptors for EGF, and suggest that EGF, in addition to PDGF, is also involved in the cell growth of VSMC.