In the ever-developing world, the recent years have brought about a wide range of novelties and significant developments in the fields of veterinary anaesthesia and analgesia. In the not-too-distant past, it was believed that the pain threshold of animals was high and that pain was not felt by animals during surgery, when they were anaesthetised. It was considered that the only analgesic drugs that could be used during operation were non-steroidal anti-inflammatory drugs. Today, these suppositions are all accepted as fallacies across the world, and it is well-known that the administration of analgesic drugs should be started in the preoperative period. This article describes pain in animals, how pain perceived by the operated animal can be recognised, and if not treated, to which complications pain may lead. Furthermore, in the last part of the manuscript, complications associated with the use of atropine and ?2-agonist combinations, and the adverse effects of anaesthesia-induced hypotension are also explained. This review is intended to provide an insight into recently developed novel practices and to elucidate some main issues, which may be confusing for the veterinary practitioner.