The distribution, size and density of the apocrine glands in hidradenitis suppuritiva as compared with those in axillary hyperhidrosis and normal controls have been studied. There are no significant differences in the size or density of the apocrine glands in hidradenitis suppuritiva as compared with normal controls. The apocrine glands in axillary hyperhidrosis are significantly larger than those in axillary hidradenitis and in normal controls. A simple method that can be used to demonstrate the distribution of the apocrine glands preoperatively is described. This has proved useful in delineating the area which it is necessary to excise to obtain complete apocrine gland excision in the diseased area. The apocrine gland-containing skin in the diseased region does not always correspond exactly to the hair-bearing area in that region.