The possible adverse effects of the application of veterinary drugs are considered with special reference to their illegal use or misuse in the different categories of animals (pet, sporting, food-producing). The risks of unacceptable drug residues in animals and their products, the environment and man are taken into consideration. The need is stressed for proper veterinary surveillance by previous assessment of priorities such as animals' health status, economic aspects, quality of food of animal origin, safeguard of the environment.