INTRODUCTION: Hirsutism is a disorder which affects about 10 to 15 percent of women. Hirsutism is the most frequent androgen excess disorder in women1. Hirsutism is defined as the excessive growth of terminal hair in androgen dependent areas of a woman’s body. The sites affected include; The upper lip, Chin, Chest, Upper abdomen, Lower abdomen, Upper back, Lower back, Upper Arm, Thighs. Each of the nine areas is given a score of 0 to 4 depending upon the grade 1 –mild, 2-moderate, 3-complete light coverage and 4 for complete heavy coverage. A score of more than 15 is considered as severe hirsutism2. Occasionally, hirsutism may signal more serious pathology. Therefore, clinical evaluation should differentiate benign causes from tumours and other conditions that require specific treatment. Hirsutism should be differentiated from hypertrichosis. Hypertrichosis is defined as a diffuse increase in vellus hair growth and is not androgen dependent. The congenital causes of hypertrichosis include Hurlers syndrome, trisomy 18, fetal alcohol syndrome etc. The other causes include hypothyroidism, porphyrias, epidermolysis bullosa, anorexia nervosa, malnutrition, dermatomyositis, severe head injury and trauma. AIM OF THE STUDY: There are not many studies that look at the causes of hirsutism, their clinical profile and hormonal changes .Therefore, this study was undertaken to analyse the clinical profile, biochemical profile, various causes of hirsutism and the response to treatment. MATERIALS AND METHODS: Study Design: This is a prospective study. Period of Study: The period of study was from August 2010 to September 2011. Place of Study: Subjects were taken from Endocrinology clinic and Fertility Research centre, Institute of Obstetrics and Gynaecology, Govt Hospital for Women and Children, Egmore. Inclusion Criteria: Females with modified Ferriman-Gallwey scoring >8 were included in the study. After getting an informed consent from the subjects, they were subjected to clinical and biochemical evaluation after history taking. Exclusion Criteria: Women who were 60 years and above and pregnant women were excluded from the study. SUMMARY: In this study, 52 had ovarian causes, (46 – PCOS, 4- ovarian tumour, 2- premature ovarian failure), one had adrenal cause (late onset CAH), systemic cause (hypothyroid -6) for hirsutism.• Majority of cases of hirsutism in this study fall in the 21 – 30 years age group. • In addition to hirsutism, menstrual irregularity is the chief complaint. • Majority had hirsutism scoring of 9 to 11. Severe hirsutism (Scoring more than > 15) was seen in androgen secreting ovarian tumour and PCOS (4 cases). • Virilization features commonly were seen in all the 4 ovarian tumors and late onset CAH . Highly elevated free testosterone levels were seen in androgen secreting ovarian tumours and late onset congenital adrenal hyperplasia. • Subjects with hirsutism were either overweight or obese except ovarian tumours and CAH. • Co morbid conditions like hyperlipidemia, diabetes mellitus, hypertension were seen in few PCOS and few non PCOS subjects. • Level of the testosterone did not correlate with the severity of hirsutism in the PCOS group. CONCLUSION: This study evaluates the various causes of hirsutism, their clinical and biochemical profile and their outcome after treatment. Although PCOS is the most common cause for hirsutism, other causes should also be thought of. The treatment should be individualised depending upon the cause of hirsutism. We should have a high suspicion of virilizing tumours if features of virilization are present. Hirsutism has a response to OCP containing cyproterone acetate but the reduction in severity of hirsutism is mild. They might need increase in the duration of treatment and dosage of cyproterone acetate. Free testosterone and DHEAS may or may not be elevated in PCOS. Majority have normal levels. Free testosterone is highly elevated in androgen secreting ovarian tumours. This study has highlighted the importance of evaluating the other causes of hirsutism such as androgen secreting ovarian tumours and adrenal hyperplasia. Hirsutism causes cosmetic problem and psychological upset on a woman. It can also be a manifestation of an underlying health problem. Hence it should be properly treated so that a favourable outcome can be obtained.