Epidermal growth factor inhibits elastin synthesis in chick aortic smooth muscle cells. The inhibitory effect was dose-dependent with a ninety percent reduction at 100 ng/ml and time-dependent with at least 6h lag phase for the expression of the effect. In contrast, collagen synthesis remained constant. The degree of inhibition in elastin synthesis was parallel to the decrease in the steady-state levels of elastin mRNA. These results indicated that epidermal growth factor specifically inhibits elastin synthesis and will be a useful suppressor for elastogenesis under pathological conditions.