A yeast, Candida sp. MK-1, newly isolated from activated sludge as a dye decolorizing microorganism, decolorized Color lndex (C.l.) Reactive orange 16 and C.l. Reactive red 21 on the solid medium. Both azo dyes were also decolorized even in the liquid medium. The decolorizing activity by Candida sp. MK-1 depends on glucose concentration. Textile stained by Reactive orange 16 or Reactive red 21 was decolorized by Candida sp. MK-1. There results suggest that Candida sp. MK-1 has potential applications for the decolorization of textile and for the bioremediation of dye-contaminated wastewater.