Background: Senile gluteal dermatosis (SGD) is a common genital dermatosis but has gained little attention before. A large-scale clinical study of this disease is lacking. Materials and methods: We examined 162 consecutive outpatients with gluteal skin diseases of different causes. Fourteen skin biopsies were performed. Patient's age, gender, body mass index (BMI), way of sitting or lying, treatment response, and underlying systemic diseases were recorded. Results: About 137 (85%) patients could be defined as SGD. These patients, with a mean age of 79.4 ± 40.7 years and a mean BMI of 21.7 ± 10.8, presented with either partial (n = 43, 31%) or full-blown (n = 94, 69%) SGD lesions characterized by the sign of so-called "three corners of a triangle": brownish plaques on the gluteal cleft and each side of the buttocks. Male/female ratio was 130/7. Itching or pain of varying intensity was reported by 50 patients (36%) and 14 patients (10%), respectively. Eighty-six patients (53%) presented with horizontal hyperkeratotic ridges, a characteristic sign of SGD. Most patients spent most of the day sitting but reported no special way of sitting or lying. More than half of patients with SGD claimed no response to topical steroids and/or keratolytics. In comparison with patients with SGD, SGD-free patients were younger (61.3 ± 36 years, P = 0.0005) and heavier (BMI 26.2 ± 15.6, P < 0.0001) but showed no significant difference in the frequency of underlying systemic diseases. Conclusions: SGD is a common dermatosis, mostly affecting the thinner elderly. Friction, pressures and long hours sitting seemed to be important factors to trigger this dermatosis.