The arginine requirement of the growing rabbit has been re-investigated and found to vary depending upon the pattern of the indispensable amino acids other than arginine. The requirement was higher on a pattern simulating isolated soy protein than on a pattern that contributed essentially the requirement pattern. The rabbit has been found sensitive to protein quality in the same way as other monogastric animals, including the rat and the chick. Interestingly, soy protein appears to provide a superior amino acid pattern to whole egg. Also, casein may be limiting in arginine for the growing rabbit.