Sjögren-Larsson syndrome (SLS) is an autosomal recessive disorder characterized by the presence of congenital ichthyosis, mental retardation, and spastic diplegia or tetraplegia. The ichthyosis is generalized in distribution, and histological features of the skin include hyperkeratosis, papillomatosis, acanthosis, and a mildly thickened granular layer. Electron microscopy shows lamellar membranous inclusions in the granular and cornified cells. SLS patients have impaired fatty alcohol oxidation caused by deficient activity of fatty aldehyde dehydrogenase, a component of the fatty alcohol:NAD+ oxidoreductase complex. This enzymatic defect provides a reliable means for diagnosing SLS patients and unaffected SLS carriers. Prenatal diagnosis of SLS can be accomplished by enzymatic studies of amniocytes and cultured chorionic villi cells, or by histological examination of a fetal skin biopsy. Although still unproven, fatty alcohol accumulation in patients is thought to be responsible for the cutaneous symptoms.