When white rats were daily fed 0.33 gms. l-phenylalanine, per 100 gms. body wt., the outcome depended upon the manner of dissolving the phenyl-alanine: (1) in equiv. quantity of HCl, (2) in aq. Na carbonate soln. up to pH 8, or (3) in equiv. quantity of NaOH. In (1), the urine contained varying amts. of phenyl-pyroracemic acid due, as found later, to d-phenyl-alanine in the preps, of l-phenylalanine used. In (2) large amts. of phenyl-pyro-racemic acid were eliminated. In (3) an alkaptone substance was eliminated: it gave all the reactions of homogentisic acid. Alkaptonuria is more easily induced in [male][male] than in [female][female].