BACKGROUND: PCOS is a common female endocrine disorder with prevalence ranging from 2.2% to 26%. Most reports have studied adult women with age ranged from 18 to 45 years. The aim of this study was to find the prevalence of PCOS in Indian adolescents.METHOD: We prospectively studied 460 girls aged 15 to 18 years from a residential college in Andhra Pradesh, South India, who underwent clinical examination. Out of which 72 girls with oligomenorrhea and/or hirsutism were invited for biochemical, hormonal, and ultrasonographic evaluation for diagnosis of PCOS by Rotterdam criteria. PCOS was defined as the presence of any two of the three features: (1) Oligo/amenorrhea: absence of menstruation for 45 days or more and/or â‰¤8 menses per year. (2) Clinical hyperandrogenism: Modified Ferriman and Gallway (mFG) score of 6 or higher. (3) Polycystic ovaries: presence of >10 cysts, 2-8 mm in diameter, usually combined with increased ovarian volume of >10 cm(3), and an echo-dense stroma in pelvic ultrasound scan.RESULTS: Out of 460 girls, one (0.22%) had oligo/amenorrhea with clinical hyperandrogenism, 29 (6.30%) had oligomenorrhea with polycystic ovaries, one (0.22%) had polycystic ovaries with clinical hyperandrogenism and 11 (2.39%) had oligomenorrhea with polycystic ovaries in the presence of clinical hyperandrogenism. Thus 42 (9.13%) girls satisfied Rotterdam's criteria for PCOS, which increased to 50.46 (10.97%) when imputed data were included.CONCLUSION: Prevalence of PCOS in Indian adolescents is 9.13%.This draws attention to the issue of early diagnosis in adolescent girls.2011 North American Society for Pediatric and Adolescent Gynecology. Published by Elsevier Inc. All rights reserved.