Background: Although the polycystic ovary syndrome (PCOS) is the most frequent endocrine disorder in women of reproductive age, its diagnosis remains one of the most challenging issues in endocrinology, gynecology, and reproductive medicine. The elevated levels of Anti-mullcrian hormone (AMH) in the women of PCOS strongly suggested that serum AMH levels may be used in the diagnosis of this condition. Laparoscopic ovarian diathermy (LOD) frequently induces ovulalion in patients with polycystic ovary syndrome (PCOS). The mechanism by which this effect occurs remains largely unexplained.The aim of this study is to assess whether AMH could play a role in the diagnosis of PCOS and to measure changes in (AMH) production in response to (LOD) to sec whether this could explain the mechanism of action of (LOD). Methods: This prospective study included 30 anovulatory women with PCOS and 10 ovulatory women as a control. All PCOS women underwent LOD. Blood samples were collected before and after LOD to measure plasma concentrations of Anti-Mullerian Hormone (AMH), cstradiol (E2), gonadotrophins (FSH and LH), and testosterone. The number of early (at day 3 of the cycle) antral follicles (2-9mm in diameter) were estimated by ultrasound scanning. Results: The mean serum AMH level was about 3-folds higher in PCOS patients than in controls (P < 0.001). Likewise, the 2- to 9-mm follicular numbers per ovary (FNPO) at U/S were 3-fold higher in PCOS patients than in controls (P < 0.001). It was significantly related to the serum AMH levels, both in controls (r = 0.370; P< 0.022) and in patients (r = 0.670; P < 0.0001). AMH was also positively related to the serum testosterone level in cases in comparison to controls (r = 0.454 and P < 0.0004 in cases; versus r = 0.163 and P = 0.288 in controls). No significant correlation was observed between FSH, E2, BMI and AMH levels in PCOS patients and controls. In PCOS patients, the mean scrum level of AMH differed significantly by ANOVA (P < 0.05) between those presenting either with amenorrhea (n = 10), oligoamenorrhea (n = 10) or regular cycles (n = 10); the former and the latter having the highest and the lowest values, respectivcly(8.17ng/ml andl6.8 ng/ml). As expected, the 2- to 9mm follicular number per ovary (FNPO )followed the same trend in these three subgroups ( P < 0.05), whereas age did not exert a statistically significant effect. Our data suggest that, high androgen (HA) is associated with higher serum AMH levels in PCOS patients with irregular cycles. Following LOD, there was a statistically significant reduction of mean plasma concentrations of AMH from the pre-operative values in the overall group of 30 women with PCOS [8.2ng/ml versus 12.2ng /ml]. Women who ovulalcd after LOD (n = 10) had a higher mean pre-LOD AMH level [15.5 ng/ml] compared with that [10.5 ng/ml] of patients (n = 20) who did not respond. After LOD there was a statistically significant reduction in LH: FSH ratio and the plasma concentrations of LH and testosterone. Plasma concentrations of FSH did not change after LOD.Conclusions: Anti-Mullerian Hormone could be a valuable marker for diagnosis of polycystic ovary syndrome and improvement of its function after laparoscopic ovarian diathermy. The dramatic and significant reduction of Anti-Mullerian hormone after LOD especially in responders makes it likely that this hormone has a role to play in the mechanism of action of LOD.