Useful cryophilic killer strains of Saccharomyces cerevisiae were bred by back-crossing KL-88, which is a wild killer sake yeast, with a repetitive parent WL-7 and is one of the best cryophilic wine yeasts. The hybrids maybe aid in producing good wines in pure cultures at relatively low temperature (13 ˜ 15°C).A haploid of KL-88 was crossed with haploids of WL-7 to yield first-generation hybrids. Haploids possessing both killing activity and S02 tolerance were selected from the hybrids and back-crossed with a haploid of WL-7 to yield second-generation hybrids. Several strains of killer hybrids were comparable to WL-7 in fermentation ability at 15°C, S02 tolerance, TTC stain, and growth on β-alanine medium at 35°C. One strain (2HYL-2) aided in producing wine as good as with WL-7, in fermentation at 15°C on pilot-plant scale.The hybrid killed only Saccharomyces yeasts in grape must. In the last-stage of fermenting Kōshū grape must with the killer hybrid (2HYL-2), no sensitive yeasts were detected, because t...