DNA fragment being able to restore in vitro activity of ${eta}-1,3-glucan$ synthase was cloned by transformation of the Saccharomyces cerevisiae LP353 mutant strain with genomic library constructed in the YCp50. For the selection of transformants which showed no detectable phenotype linked to recovery of the defect in ${eta}-1,3-glucan$ synthase activity, the colony autoradiography was succesfully applied. The restriction map of the cloned DNA fragment, which is 8.5-kb in length, was constructed. Both the YEplac195 and the YCp50 carrying the 8.5-kb fragment increased ${eta}-1,3-glucan$ synthase activity of LP353 by two fold. Neither the YEplac195 nor the YCp50 carrying the 8.5-kb DNA fragment, however, complemented the temperature-dependent osmotic sensitivity which is another distinctive phenotype of LP353. Subcloning experiments indicated that a functional region was located in 4.8-kb BglII-KpnI fragment. The 4.8-kb fragment was also able to increase the level of ${eta}-1,3-glucan$ content in cell wall as well as the resistance of cells to cell wall lytic enzyme, ${eta}-1,3-glucanase$. The growth rate of the LP353 with 4.8-kb fragment was almost same as that of wild type strain in liquid medium with 1.2 M sorbitol at nonpermissive temperature. Taken these results together, the 4.8-kb fragment seemed to contain the BGS2 gene for ${eta}-1,3-glucan$ synthase activity in yeast S. cerevisiae.