This research project was performed to identify and quantify the contaminants remaining in used HCFC and CFC refrigerants produced by recycling techniques employing oil separation prior to the filtering process. To determine the effects of contaminants on the chemical stabilities of used CFC and HCFC refrigerants, before and after recycling, sealed tube tests were performed at 100°C for seven days with R-l 1 refrigerants and at 175°C for 14 days with R-12, R-22, and R-502 refrigerants. The sealed tube tests were run with copper and valve steel coupons to accelerate the effects of the contaminants. Three main levels of contamination were studied; (1) fresh refrigerant, (2) used refrigerants containing minimum (normal service) and maximum (motor burnouts) levels of contamination, and (3) recycled refrigerants produced from the used refrigerants (normal and burnouts). Used lubricating oil samples obtained from normal service and motor burnouts were added to the fresh refrigerants prior to heating in the sealed tubes in an attempt to determine the maximum allowable levels of oil in recycled refrigerants for continued use.