Biodegradation of phenol and monochlorophenols (CPs) by a yeast strain of Rhodotorula glutinis was examined. The strain completely degraded 5 mM of phenol and utilized phenol as a sole carbon source. The strain may degrade phenol by the “ortho” type of ring fission because muconolactone was observed in the cultured broth. 3-Chlorophenol (3-CP) and 4-chlorophenol (4-CP) were well degraded and stoichiometric release of chloride ion was observed, but degradation of 2-chlorophenol was low with a small quantity of chloride ions. Biodegradability of 3-CP and 4-CP was increased by the addition of phenol or CPs to the medium at the cell cultivation. Since 4-chlorocatechol and maleylacetic acid were determined as metabolites of 3-CP and 4-CP by GC/MS analysis, dechlorination may take place between the formation of 4-chlorocatechol and maleylacetic acid.