A diagnosis of scleroderma and phenylketonuria was made in an 18-month-old girl. This is the third recorded incidence of the association of these two disorders. Following institution of a low phenylalanine diet, there was softening of the severe sclerodermatous lesions on the trunk and lower extremities, although new lesions have slowly developed on the upper extremities. There has been no clinical or laboratory evidence of systemic scleroderma. Urinary chromatographic studies on 9 other children with scleroderma failed to reveal any distinctive abnormalities in the excretion of amino acids, phenols, indoles, or imidazoles.