In most of South Asia, prevalences and phenotypes of polycystic ovary syndrome (PCOS) among women in the community are unknown. The authors aimed to estimate prevalence and phenotype in a community setting in Sri Lanka and to test a valid, feasible screening approach to early diagnosis. A community-based, cross-sectional study was carried out in 2005-2006. A random sample of 3,030 women aged 15-39 years was selected by cluster sampling proportionate to population size. An interviewer-administered questionnaire was utilized to screen for "probable cases" of PCOS based on menstrual history and clinical manifestations of hyperandrogenism. Selected "probable cases" underwent clinical, biochemical, and ovarian ultrasound assessment. The response rate was 96.2% (n = 2,915). A total of 220 (7.5%) "probable cases" were identified: 209 women with oligo/amenorrhea (95%) and 11 women with hirsutism (5%). Further evaluation of the 220 probable cases confirmed 164 newly diagnosed cases of PCOS based on the 2003 Rotterdam diagnostic criteria. With 19 previously diagnosed cases already present, total prevalence was 6.3% (95% confidence interval: 5.9, 6.8). Of the women with "oligo/amenorrhea and/or hirsutism," 91.1% were confirmed to have PCOS; 99.4% of women with "regular cycles in the absence of clinical hyperandrogenism" were confirmed as normal. The most common phenotypes of PCOS were oligo/amenorrhea and polycystic ovaries (91.4%) and oligo/amenorrhea and hirsutism (48.3%).