A relationship between very high isobutyl alcohol production and autolysogeny of cells was found in single spore Saccharomyces cerevisiae cultures. Autolysis in autolysogenic cultures occurred at low temperatures (25-degrees-5-degrees-C) as well as at high temperatures. Autolysogeny was always segregated at a 2:2 ratio from a natural strain. This indicates that it is a hereditary, monogenic, and recessive character.