Background: Pilonidal sinus (PS) is a chronic inflammatory disease which is characterized by a granulomatous reaction to fragments of hair shaft penetrating epidermis from the cutaneous surface. The present study was conducted to assess etiological factors in umbilical pilonidal sinus. Materials & Methods: 58 cases of umbilical pilonidal sinus of both genders were enrolled. Patients were put in group I and healthy subjects in group II (control group). Parameters such as body mass index, profession, skin colour, personal history of PS, family history of PS, how frequently they take a bath, and whether they wear tight clothes and use belt.