The thermo-oxidative degradation of unstabilized and stabilized coatings of each of a saturated polyester and a poly (pentaerythritol-phthalate)based alkyd coatings separately pigmented with syncomine yellow 1630 have been studied. The test stabilizer was dibutyltin diethanoate employed at varying concentrations. The degradation of the coatings was monitored using color development, determination of gel content, stress-strain relationships, gloss retention and optical microscopy. The results showed that incorporating a concentration of 5 or 10 x 10-4 mole % of the tin ester can effectively stabilize both the polyester and alkyd coatings against thermo oxidative degradation.