Long or tailored lifetime, bio-degradability as well as fire behaviour are important properties of polymer materials. Thus controlling the degradation by effective stabilization or reducing fire risks by flame retardants are important tasks in the design and development of polymeric materials when polymers are subjected to fire, heat, oxygen, sunlight or humidity. Corresponding phenomena, mechanisms and structure-property-relationships must be understood if the technology and application of polymers are to continue to advance. Given an overview and starting the discussion within this framework is therefore a major function of this lecture. - physical and chemical ageing of polymers - decomposition of structure and degradation of properties - thermal and thermo-oxidative decomposition - photo-oxidation, ozone induced degradation - hydrolysis, bio-degradation - weathering - chemistry of stabilisation and corresponding additives - lifetime prediction - fire behaviour: ignition, flame spread, heat release rate and fire load - flame retardancy mechanisms and flame retardants close