An analysis was made of the causes of death in horses and ponies over one year of age which died suddenly (Group 1) or were found dead but were considered normal when last seen (Group 2). There were 49 animals in Group 1. Thoroughbreds were overrepresented, but there were no ponies in this group. No cause of death was found in 30.6 per cent of cases and 16.3 per cent died from each of the following causes: haemorrhage in the respiratory system, central nervous system, and adverse drug reactions. Cardiovascular lesions were the cause of death in 14.4 per cent and the remaining 3.1 per cent had lesions of the gastrointestinal system. Racehorses mostly died suddenly from severe haemorrhage in various sites, particularly the thorax. In Group 2 there were 151 animals, and in 33.1 per cent no cause of death was determined. Gastrointestinal lesions were considered the cause of death in 39.2 per cent of cases and respiratory lesions killed 8.6 per cent. Lesions of both the central nervous system and cardiovascular system were considered the cause in 4.6 per cent of cases. The remaining 9.9 per cent of animals had miscellaneous lesions. Toxicological studies were performed in 46 of the total 200 cases, and only two had positive results; lead in one and nicotine in the other.