Kluyveromyces marxianus TS87, which was isolated in our laboratory, was found to have better growth and fermentative abilities at high temperature when compared to the fermentative yeast Saccharomyces cerevisiae TS8. Breeding of K. marxianus TS87 was performed by protoplast fusion to enhance its fermentation ability at high temperature. During the experiment, 40 fusants were obtained. They were stable during subculture and classified into three groups in accordance with the characteristics of the parental strains. F-1, a fusant of Group 1, was superior to the parental strains in its high temperature growth and fermentation abilities due to its growth velocity. However, the fusant F-1 lacked the thermostability of S. cerevisiae TS8.