Killer yeasts which showed killer activity toward Candida glabrata IFO 0622, Saccharomyces cerevisiae Y 15, and S. cerevisiae Y-222, were isolated in the process of Ki-moto making. The isolates showd no killer activity toward S. cerevisiae Kyokai No.7. Each isolate didn't show killer activity to all other isolates.The killer yeasts accounted for about 50% of the total wild yeasts on the 4th day of the Ki mob but were not detected at the mid to the late stage of the Ki-moto making. All of the isolated killer strains were found to be film-forming yeasts. Most of them showed high killer activity and were identified as Pichia anomala. And these killer strains showed high killer activity to Zygosaccharomyces rouxii IFO 0505 in the presence of NaCl. The results indicated that the killer yeasts seemed not only to be harmless during the sake brewing process but also to have much the same spectra of killer activity against sensitive yeasts in the eary stage of Ki-moto making.