Silk fibroin from a domesticated mulberry silkworm, Bombyx mori, is the most widely used in biomaterial design. We report for the first time the preparation of a relatively smooth (granule free) film of the nonmulberry Samia cynthia ricini fibroin for comparative evaluation of its cell-supporting properties against those of the B. mori fibroin film. The granule formation on the S. c. ricini fibroin film was successfully prevented by facilitating proper rearrangement of the protein molecules, as monitored by FT-IR, by dialysis through a stepwise decrease in the urea concentration in the dialysis media. The lower contact angle of the S. c. ricini fibroin film, compared to the B. mori fibroin film, corresponds well to its lower hydrophobic/hydrophilic amino-acid ratio and grand average of hydropathicity (GRAVY). L929 murine fibroblast cells on the granule-free S. c. ricini fibroin films exhibited greater proliferation and spreading rates than those on the B. mori fibroin films, possibly attributable to its higher content of hydrophilic and positively charged amino acids. It further suggests that fabrication, modification and/or engineering of S. c. ricini fibroin may provide a better biomaterial scaffold design than the more commonly used B. mori fibroin.