This chapter examines some of the research on environmental enrichment and training that has been conducted in zoos on a range of taxa, and includes some work that has been done in other captive environments. When animals are kept in barren environments in captivity they are liable to develop abnormal behaviours. Some of these are repetitive and some involve self-injury. Providing complex and diverse environments helps to prevent or reduce the occurrence of these behaviours and, in recent decades, experiments on environmental enrichment have contributed to positive animal welfare in zoos. Alongside these developments advances have been made in the training of animals and our knowledge of the part that this may play in their welfare and educational value.