The occurrence of stereotypies in animals is primarily related to (i) internal states induced by the captive environment or other external stimuli that continuously trigger or motivate specific behaviours, (ii) situations in which the environment causes a state of chronic stress that influences the path from the cortex to the basal ganglia promoting and sequencing a behaviour that results in a lack of proper inhibition and (iii) an experience in early ontogeny that influenced the development of the central nervous system, causing inappropriate sequencing and a lack of inhibition with effects visible even in adult life. Such features of stereotypic behaviour as its repetitiveness, a gradual loss of variability and increasing predictability might be related to positively reinforcing opioid effect, environment predictability or synaptic priming. Consequences of stereotypies are various and depend on their causes and the types of stereotypic movements. They might influence the physical state of the animal, handicapping its social interactions, but also decrease anxiety and ability to react to external stimuli. Stereotypies and their consequences are strictly related with other welfare indicators and are unequivocally treated as a symptom of abnormality.