During a 5-week trial, no beneficial effect on growth or efficiency of feed utilization was obtained when either inositol or biotin was added to the basal ration which contained the six B-complex vitamins — thiamine, riboflavin, niacin, pyridoxine, pantothenic acid, and choline. The addition of sulfaguanidine, at the levels fed, had no appreciable effect on the inositol and biotin requirements of the pig. The following syndrome developed in the pig when sulfathalidine was added to the basal ration: spasticity of hind legs, hair loss, dermatosis of the skin characterized by dryness, roughness, and a brownish exudate, exudate around eyes, and cracks in feet. The syndrome was prevented when biotin was added to the basal ration. This syndrome is similar to that produced with the pig fed desiccated egg white and prevented by intramuscular injection of biotin. The addition of inositol to the basal ration plus sulfathalidine alleviated to a large extent the deficiency symptoms prevented by biotin. A possible explanation is that inositol acted indirectly by stimulating intestinal synthesis of biotin. Biotin and inositol are concerned with the efficiency of feed utilization, since a lack of these two vitamins, when sulfathalidine was fed, resulted in smaller gains being obtained when the same amount of feed was eaten by the pigs.