THE PRESENT RAPID developments in drug therapy pose a serious problem for the busy practitioner-young or old. The older veterinarian may recall with some nostalgia how his training in therapeutics involved a comparatively few "tried and true" drugs with which he entered his practice. New drugs appearing at relatively infrequent intervals were added to his armamentarium and he had time to evaluate them for himself more or less at leisure. These were then added to his "Materia Medica" or discarded. Recent advances in all phases of medical sciences began to add many new words to his professional vocabulary and his interpretation of new drug activities had to be evaluated in terms of vitamins, endocrines, chemotherapy, antibiotics and a host of other developments based on a more intimate knowledge of the intricate nature of physiological mechanisms. In the light of this newer knowledge, synthetic drugs are now almost tailor-made for specific clinical entities while some of the old stand-bys have undergone refinement with increasing potency. Newer vogues in medication, particularly the increased use of parenteral drug administration, have also added to the problem. The experienced clinician can sympathize with the recent graduate and the student who must face the same problems in drug evaluation with very limited experience to draw upon. An added harassment, particularly to the already overcrowded student, has been the adoption of the metric system in dosage computations as "official" in the United States Pharmacopeia and the National Formulary. Since the apothecary system is still widely used, conversions between the metric and apothecary systems must be learned.