The prevalence of feeding practices and supplements for dogs used in private practice (pp) and the non-profit-making People's Dispensary for Sick Animals (pdsa) was evaluated. Questionnaires were completed by 400 pp clients and 400 pdsa clients, of which 27·2 per cent and 29·8 per cent, respectively, gave supplements to their dogs. Fatty acids/oils were given by 10·3 per cent of pp clients and 11·5 per cent of pdsa clients, glucosamine and/or chondroitin by 10·5 per cent and 5·8 per cent, and vitamins by 6·8 per cent and 19·3 per cent, respectively. The supplements were provided daily by 17·8 per cent of the pp clients and 14·3 per cent of the pdsa clients, and the pdsa clients were 50 per cent more likely to provide the supplements only weekly or monthly than the pp clients. A commercially available maintenance or dietetic diet was fed by 98·8 per cent of the pp clients and 94·2 per cent of the pdsa clients.