Cephalosporium sp. KM388 produced two kinds of extracellular alkaline proteinases (C and D) in complex medium. Proteinases C and D were purified 263 and 195-fold, respectively, to an electrophoretically homogeneous state from the culture broth by hydrophobic adsorption on Butyl-Toyopearl 650M with 30% saturated ammonium sulfate and .chromatographies on DEAE-Sepharose CL-6B, DEAE-Toyopearl 650 M, CM-Sepharose CL-6B, and Sephadex G-75. The molecular weights of proteinases C and D were 22, 000 and 24, 000, respectively, by gel filtration. The isoelectric points were observed as pI > 10.5 for proteinase C and pI = 3.8 for proteinase D. The pH optima for the proteolytic activity of proteinases C and D were 11 and 10, respectively. Proteinase C was unstable below pH 10 but was stabilized by Ca2+ or Mg2+. Proteinase D was stable above pH 7. Proteinase C was inhibited only by Hg2+, but proteinase D was inhibited by Mn2+ and Zn2+ in addition to Hg2+. Both proteinases were inhibited strongly by chymostatin, weakly by DFP and PMSF, but little by PCMB, MIA, EDTA, and SDS. These enzymes showed very high activity against BTEE but low activities against BAEE and TAME as well as Bz-ala-OMe.