One sheep metabolism and three sheep growth trials were conducted to evaluate diammonium phosphate as a source of phosphorus or nitrogen. In the sheep matabolism trial, diammonium phosphate was found to be a satisfactory source of phosphorus, but the nitrogen of this compound was not retained as well as that supplied by urea or soybean meal; higher urinary nitrogen excretion was found in sheep fed diammonium phosphate. Considerable difficulty was experienced in obtaining adequate feed consumption on rations containing diammonium phosphate. Laboratory tests indicated that diammonium phosphate will release ammonia when placed in contact with distilled water or ruminant saliva and it is suggested that the odor of ammonia was the cause of reduced feed consumption when the sheep diets contained diammonium phosphate. When the diets were pelleted in the fourth trial, there was a significant loss of dietary nitrogen as ammonia, and no loss from the control diet. The results indicate that under heat and pressure, about 50% of the nitrogen supplied by diammonium phosphate was lost in the pelleting process. One cattle metabolism and two cattle maintenance trails were conducted to evaluate DAP as a source of nitrogen or phosphorus and the results were in conformance with those obtained in the sheep trials. The toxicity trials indicate that 88 gm. of diammonium phosphate per 100 lb. (equivalent to 40 gm. of urea) of body weight is toxic to sheep.