For a very long time the introduction of veterinary pharmaceutical specialities has not posed great problems for the manufacturers at least not in the European market. Nevertheless many amongst them have devoted themselves to detailed preliminary studies notably in the pharmacological, toxicological and chemical fields. However, the scope of these preliminary studies was often adjusted to the speciality and to the development costs in relation to the size of the market, that was envisaged. Studies along the lines imposed by the F.D.A. were carried out only if and when a product showed a sufficiently promising future to allow for hope of success on the U.S. market. Since four years the situation has changed and for a number of reasons.