A syndrome of hereditary hypotrichosis with an unusual natural history and clinical features was encountered in a Caucasian family of four generations with a total of twenty-four members of whom eleven were affected. The mode of inheritance was autosomal dominant with variable penetrance. The loss of hair involved the scalp, eyebrows, eyelashes and body hair, manifesting itself in the school years and progressing to almost complete baldness. There were no associated abnormalities and no sex limitation. Clinical, genetic, biochemical, mechanical, histological and immunological aspects were studied. Essential differences between this type of hereditary hypotrichosis and others previously recorded are stressed.