A feature article is presented on recent developments in the investigation of stimuli responsive polymers and their biomedical applications. Polymer systems are grouped with respect to sensitivity to changes in temperature, pH, light, redox potential and other special changes in environment. Underlying principles and possible applications of various systems are discussed. Critical evaluation of all benefits but also drawbacks of a particular stimuli responsivity is therefore necessary when planning the construction of multi-stimuli responsive systems. Special focus is devoted to biological consequences of physico-chemical properties of the polymer materials.