Chlorine species used as disinfectants in tap water have a deteriorating effect on many materials including polyethylene. There are only very few scientific reports on the effect on the effect on polyethylene pipes of water containing chlorine dioxide. Medium-density polyethylene pipes stabilized with hindered phenol and phosphite antioxidants were pressure teated with water containing 4 ppm cholorine dioxide at 90 C and pH=6.8 as internal medium. The stabilizers were rapidly consumed towards the inner pipe wall; the rate of consumption was four times greater than in chlorinated water at the same temperature. The depletion of stabilizer occurred far into the pipe wall. A supplementary study on a polymer analogus (squalane) containing the same stabilizer package showed that the consumption of the phenolic antioxidant was 2.5 times faster when exposed water containing chlorine dioxide than on exposure to chlorinated water. The subsequent polymer degradation was an immediate surface reaction.