Hirsutism is a common clinical problem in women and the treatment depends on the cause of hirsutism. The study was designed to determine the various causes of hirsutism and their prevalences in a Turkish population. 168 women with hirsutism attending to Endocrinology Outpatient Clinic of Erciyes University Hospital were investigated in detail. Medical history, physical examination, and basal levels of free testosterone (IT), androstenedione, follicle-stimulating hormone (FSH), luteinizing hormone (LH), dehydroepiandrosterone-sulphate (DHEAS), 17 hydroxyprogesterone (17-OHP), 11-deoxycortisol (11-S), thyroid hormones, thyroid stimulating hormone (TSH), and prolactin were determined. ACTH stimulation test was performed for the diagnosis of non-classic congenital adrenal hyperplasia (NCAH). Pelvic/vaginal and adrenal ultra sonographics were performed for the detection of tumors and polycystic ovarian changes. Polycystic ovary syndrome (PCOS) was diagnosed in 96 (57.1%) patients, idiopathic hirsutism in 27 (16%), NCAH in 12 (7.1%), adrenal carcinoma in 3 (1.8%), and Cushing's disease in 1 (0.6%) patient. Among patients with NCAH, 11 (91.7%) patients had 11-beta hydroxylase (11-beta OH) deficiency, and 1 (8.3%) had 21-hydroxylase deficiency. The etiology of hyperandrogenemia was not clear in 29 (17.4%) patients and these patients were named as idiopathic hyperandrogenemia. The clinical presentation of 11-beta OH deficiency is indistinguishable from that of other hyperandrogenic states and ACTH stimulation test is the only way to diagnose this entity. Although PCOS is the most common cause of hirsutism, it is notable that nearly one fifth of hirsute women have no apparent cause of hyperandrogenernia.