We report two cases of Apert's syndrome, each of whom developed the severe acne in adolescence which is a feature of this disorder. Both responded to isotretinoin therapy. Immunohistochemical techniques, using a mouse monoclonal antibody, were employed to stain sebocyte androgen receptors in the two patients, and in five controls. This showed no difference in the number of cells with androgen receptor expression between the patients with Apert's syndrome and controls. These results support the concept that the underlying problem in Apert's syndrome is an abnormal sensitivity to normal circulating levels of androgens, and not an excess number of androgen receptors.