Assessment of pain in animals is neither easy nor, often, intuitive. Usually, vets make observations of behaviour in order to assess their patients' well-being. They must however bear in mind that pain is a subjective experience that varies greatly between individuals. The expression of pain behaviour is also highly species specific. Pain behaviour is influenced by many extrinsic factors, such as previous conditioning, social dominance and overall health status, which may contort the observations. Finally, since animals cannot verbally describe their pain, bias of the observer is inevitable. Therefore knowledge of an individual's behaviour and the assessor's observational skills and attitude towards pain will influence how pain is assessed and consequently managed.