The degradation of diethylene glycol terephthalate (DTP) and polyethylene terephthalate fiber (PET fiber) by microbes and lipase was studied. The HPLC method was used to determine the degradation ratio and degradation rule of DTP. Greater than 90% DTP was degraded by microbes in 24 clays and 40% by lipase in 24 h. The degradation of DTP call be described by the first-order reaction model. Although the biodegradation ratio of PET fiber was still weak, we demonstrated with SEM micrographs and HPLC analysis that microbes and lipase could act on the PET fiber and there were some cracks on the surface of the fiber. (C) 2004 Wiley Periodicals, Inc.