A total of 85 members of a family in which several individuals presented with hypodontia, hypotrichosis, and hypohidrosis were examined. Of these, 77 were evaluated clinically and the results compared with those obtained in an equal number of carefully chosen controls. The main symptoms among the affected males and females involved changes in the quantity and texture of head hair and in the distrubution of body hair. More than half of the males also showed precocious baldness, and 6 of them had dyskeratosis. The average of missing teeth was 12 among men with the syndrome, but only 2 among the obligate female carriers. The sweat pore counts were lower in the two sexes (42% and 60% of the normal values, respectively), and a much higher degree of asymmetry was observed especially among the affected women. Inheritance of the syndrome seems to be the result of a dominant sex-linked gene with 78% to 87.5% penetrance in the females. Genetic data concerning anhidrotic ectodermal dysplasia are still unsatisfactory; new, more detailed studies are needed, in which special attention is given to the female carriers.