Mycobacterium smegmatis SMDU produced galactitol from D-galactose in a cultivation medium containing 15% TSB (trypto-soya broth) and 1% carbohydrate. The transformation rate was highest (70% or more) in the presence Of D-glucose as a carbon source. Similar transformation results were obtained when beta--galactosidase treated whey was used in the medium instead of D-glucose and D-galactose. After the first transformation in the cultivation media, washed cells were used again for transformation, and a considerable amount of galactitol was accumulated in the reaction mixture. This study revealed that after lactose is split by beta-D-galactosidase, whey can be used directly without further separation or purification for the production of galactitol.