Abstract:It is now widely accepted that animals are able to experience pain in a similar way to humans. Acute and/or chronic pain is associated not only with many surgical procedures, but also with various medical diseases, where pain may increase morbidity and mortality. Moreover, some types of pain (e.g., neuropathic pain) can be considered as an illness in themselves. Recognizing pain and assessing its intensity are both essential for its effective management: If pain is not recognised, then it is unlikely to be treated. Two major problems account for the difficulties in pain diagnosis in veterinary patients: (1) animals are not able to verbalise and cannot refer to the state of pain they are experiencing and (2) almost all animal species tend instinctively to mask signs of pain and weakness. Therefore, pain recognition in a diseased animal may be challenging. However, practitioners can rely on different strategies, which can be put in place to reveal the presence of pain in their patients. A presumptive diagnosis, a clinical exam, the evaluation of psychomotor changes and pain expressions, the attribution of pain scores and the response to therapy are all tools which, especially when used in combination, can help the veterinary practitioner recognise a subject suffering from pain and allow a correct approach to therapy. This review summarizes the current available information regarding the methodology that could be applied in small companion animals for a correct diagnosis of pain, offering veterinarians with some "easy to use" tools to apply in their daily practice.