The effects of important medium components such as carbon, nitrogen sources and amino acids on the production of cyclosporin A(CyA) were investigated in an immobilized fungal cell fermentation using Tolypocladium inflatum. As carbon sources in the synthetic medium, fructose and maltose stimulated CyA production remarkably compared to glucose when ammonium sulfate was supplemented as a nitrogen source. In the absence of ammonium sulfate in the medium, however, CyA biosynthesis was reduced considerably without regard to C-sources tested. Ammonium sulfate was found to be the best N-source, and also ammonium phosphate and ammonium citrate showed some positive effects on CyA production. Optimum concentration of ammonium sulfate was 10g/L, and supplementation of ammonium sulfate at the start of fermentation was found to be the most efficacious for maximal production of CyA. Among the constituent amino acids of cyclic peptide, CyA, L-valine had the most significant effect on the biosynthesis of CyA, and maximum CyA production was observed when 10 g/L of L-valine was initially added.