The objective of the present study was to estimate the prevalence and and characterize clinical phenotypes of PCOS. A total of 312 women from 18 to 45 years of age working engaged in Moscow enterprises were examined in 2009. All of them were interviewed by questionnaire, underwent routine medical examination, anthropometry and blood sampling for the measurement of Prl, TSH, FSH, testosterone, 17-OP, and DHEAS levels. The degree of hirsutism was assessed using the modified Ferriman-Galway scale. Women with fewer than eight cycles during a year were regarded as having menstrual problems. All women presenting with disturbances were invited for verification of the diagnosis. PCOS was diagnosed based on the Rotterdam (2003) criteria (the presence of oligo-/amenorrhea and clinically manifest hyperandrogenism (hirsutism), with all other disorders simulating the clinical picture of PCOS being excluded). All patients with clinical signs of PCOS were examined at the Endocrinological Research Centre. They were divided into the following groups: 1. Regular menstrual cycles in the absence of hirsutism. 2. Menstrual dysfunction (oligo-/amenorrhea) without hirsutism. 3. Hirsutism without menstrual disturbances. 4. Menstrual dysfunction plus hirsutism. Mean age of the women was 30,2±7,4 years, their BMI 24±5,5, overweight patients comprised 17,3% of the total (n=54), obesity occurred in 14.7% (n=46), oligoamenorrhea in 12.8%, hirsutism in 9.3%, acne in 6.4%, infertility in 2.6%, obesity in 14%. Menstrual dysfunction without hirsutism was documented in 17/312 (5.4%) cases. The prevalence of PCOS in this phenotypical group was estimated at 17.6%. Hirsutism in the absence of menstrual dysfunction was diagnosed in 8/312 (2.6%) women (prevalence of PCOS 62.5%), menstrual dysfunction plus hirsutism in 21/312 (6.7%) patients (prevalence of PCOS 85.7%). The study has demonstrated that the overall prevalence PCOS in the given population was 6,4%, but individual symptoms of this condition were manifest much more frequently than that. It is concluded that the diagnosis of PCOS is most reliably confirmed by the presence of combination of oligo-/amenorrhea and hirsutism.