The field of polymer research is progressing rapidly from passive materials providing a certain set of properties to active polymers, which provide, receive and respond to signals from their environment. This includes interactions with molecules, biological systems and physical stimuli. Research in active polymers has been driven by an increasing demand for intelligent materials, especially in biomedical and aerospace applications. Progress in synthesis, analytics and molecular modeling enable scientists to develop active polymer systems in a knowledge-based approach. Biological systems might serve as blueprints for biomimetic and bionic solutions, leading to innovative materials concepts. Emerging active polymers respond to a range of stimuli, from changes in pH and temperature, to light and magnetic fields. Remote and on-demand control is also envisioned. Contributors discuss shape-memory polymers; shape-changing polymers; responsive hydrogels; stimuli-sensitive systems; intelligent polymers in biological systems; polymer-based actuators, sensors, and switches; active surfaces; and biomedical applications of active materials, especially for tissue regeneration and controlled drug release.