Anhidrotic ectodermal dysplasia (AED) is characterized by a well-known tetrad of anhidrosis, hypotrichosis, hypodontia, and typical facies with a wide constellation of developmental defects of tissues derived from the ectoderm. Most of these patients have normal or borderline normal intelligence, but some present with mental retardation. A 15-year-old boy and his younger brother were evaluated for dry skin and intolerance to heat since their births. Their parents and other brother were normal. Both of them had atopic dermatitis. A skin biopsy was done on their left axilla, which showed a few immature eccrine glands in the dermis. We report herein two rare cases of AED in siblings with atopic dermatitis.