We report a 5-year-old boy affected with the Tay syndrome, and give a review of 12 pertinent cases previously reported under various designations. The Tay syndrome is a distinct type of congenital ichthyosis characterized by a peculiar anomaly of hair growth which has been termed trichothiodystrophy. The hair shafts are extremely brittle, and they show alternating light and dark banding when examined microscopically between polarizing filters. Other features of this syndrome are low birth weight, short stature, mental retardation, delayed neuromuscular development and other CNS anomalies, dysplasia of nails, hypoplasia of subcutaneous fatty tissue, prematurely aged facial appearance, hypogonadism, cataracts, osteosclerosis, dysphonia, and increased susceptibility to infections. The syndrome is inherited as an autosomal recessive trait. We delineate the criteria for distinguishing this gene defect from other types of congenital ichthyosis associated with disturbed hair growth, as well as from other types of trichothiodystrophy which are not associated with ichthyosis.