OBJECTIVE: To evaluate correlations between serum anti-Mullerian hormone (AMH) levels, phenotypes of polycystic ovary syndrome (PCOS), obesity, and metabolic parameters in patients with PCOS. METHODS: A total of 175 patients with PCOS were diagnosed according to the Rotterdam Consensus were included. Exclusion criteria were age over 40, FSH>25 mIU/mL, and 17a-OHP>1.5 ng/mL. The Phenotypes of PCOS were divided into a severe form (oligo-anovulation, ANOV/hyperandrogenism/polycystic ovary morphology [PCOM]; n=59) and a mild form without HA (ANOV/PCOM, n=105). The serum AMH levels were classified into 3 groups (<5 vs. 5-10 vs. >10 ng/mL). Obesity was defined as body mass index (BMI) > or =25 kg/m2 (n=34). RESULTS: The mean age was 25.9+/-5.7 year and mean AMH level was 10.1+/-5.4 ng/mL. The BMI (kg/m2) was higher in group 1 (24.2+/-6.3) than in group 2 (21.9+/-4.3, p=0.046) or group 3 (21.6+/-3.3, p=0.019). There was no difference among the three groups in age, menstrual interval, antral follicle counts, androgens, or other metabolic parameters. The obesity group showed significantly lower AMH (7.7+/-3.9 ng/mL vs. 10.7+/-5.6 ng/mL), p=0.004) and low-density lipoprotein levels (93.1+/-21.2 mg/dL vs. 107.5+/-39.3 mg/dL, p=0.031), and showed higher total T (0.74+/-0.59 ng/mL vs. 0.47+/-0.36 ng/mL, p=0.001), free T (2.01+/-1.9 vs. 1.04+/-0.8 pg/mL, p=0.0001), and free androgen index (6.2+/-7.9 vs. 3.5+/-3.0, p=0.003). After controlling for age factors and BMI, the serum AMH levles did not show any significant correlations with other hormonal or metabolic parmeters. CONCLUSION: For PCOS patients under the age 40, serum AMH is not negatively correlated with age. High serum AMH levels can not predict the phenotype of PCOS and metabolic disturbances in PCOS patients in the non-obese group. Further study might be needed to define the relation more clearly.