A 5-year-old boy had two X-linked recessive disorders, hypohidrotic ectodermal dysplasia and X-linked ichthyosis. His mother and two older sisters were identified as heterozygotes although they appeared normal on physical examination. A decreased sweat pore count, frequently found in carriers of hypohidrotic ectodermal dysplasia, was demonstrated in all three individuals. Additionally, they had the deep corneal dystrophy of X-linked ichthyosis that has been observed not only in affected males but also in a high percentage of heterozygous females. Identification of the mother and sisters of the proband as heterozygotes enabled us to provide more effective genetic counseling for this family.