The attachment and growth of fibroblast cells (L-929) on matrices of silk fibroin from Bombyx mori domestic silkworm (DSF) and Antheraea pernyi wild silkworm (WSF) were studied by a cell culture method. The performance of the two kinds of silk fibroin was compared to that of collagen. DSF exhibited as high a cell attachment and growth as collagen did. The cells attached to DSF were extensively spread out and their filopodia were visible in the SEM pictures. WSF, which contains the tripeptide sequence Arg-Gly-Asp (believed to be a specific interaction site for cell-attachment), displayed much higher cell attachment and growth compared to DSF. The cells attached on WSF became virtually flat and their filopodia could be seen, indicating that the cells were very strongly held on the surface.