The degradation of polycondensation polymers can be due - like all the other polymers - to the thermomechanical stress acting on the melt during processing, but also to the presence of humidity that gives rise to hydrolytic chain scission. This degradation is, for the polycondensation polymers, the most dangerous giving rise to a rapid reduction of the molecular weight and then of all the final properties of the material. In addition, the eventual presence of oxygen can further increase the degradation rate, thus exalting the worsening of the material. The processing of the poly-condensation polymers is usually made with materials well dry, both because are directly processed using originally as received polymers or because they are dried before processing. Of course, the first technique cannot be used for recycled polymers and the second method is quite expensive for these cheap secondary plastics. Other methods able to avoid the hydrolytic degradation and rather able to enhance the properties of these secondary materials can strongly improve the recycling of the polycondensation polymers. In this chapter a review of the experimental results obtained on this subject is presented. The optimization of the processing conditions and/or the use of specific additives can avoid both the drying before processing and the thermo-oxidative hydrolytic degradation. In some cases an increase of the molecular weight is observed. Several examples of different polycondensation polymers are presented.