OBJECTIVES: To perform a meta-analysis of the clinical and biochemical outcomes of N-Acetyl Cysteine (NAC) in women with polycystic ovary syndrome (PCOS). METHODS: Systematic review of pertinent studies was conducted by using bibliographic databases such as MEDLINE (Ovid), CENTRAL, EMBASE and PsycInfo(inception to Nov 2012).  References of selected articles were either hand-searched and by using PROQUEST and Web of Science.  The review included randomised controlled trials with women participants having PCOS and undergoing treatment with NAC alone or in combination with ovulation induction methods like clomiphene citrate (CC) or gonadotropin injections, or in vitro fertilization (IVF).  RESULTS:  Out of 182 retrieved reports, eight studies (900 women) were included.  Three studies compared NAC (n=179) to metformin (n=177) while five studies compared NAC (n=272) to placebo (n=269).  Compared to placebo, NAC improved pregnancy rate (pooled odds ratio, OR: 3.97, 95% CI: 2.07, 7.59, 3 trials, 377 women, P<0.0001; I2: 53%), ovulation rate (OR: 4.49, 95% CI: 2.86, 7.04, 3 trials, 353 women, P<0.0001; I2: 85%) and live birth rate (OR: 3, 95% CI: 1.05, 8.60, 1 trial, 60 women, P = 0.04).  However, compared to metformin, NAC did not improve pregnancy rate, resumption of menstruation cycle, body mass index or testosterone level.  NAC was signifianctly associated with lower ovulation rate (OR: 0.13, 95% CI: 0.08, 0.22, 2 trials, 253 women, P <0.0001; I2: 0%) compared to metformin.  On the other hand, compared to NAC, metformin  improved glucose and insulin resistance profiles.  Also, when used alone or in combination with clomiphene, NAC did not significantly improve the anthropometric characteristics, testosterone levels, and lipid profiles compared to placebo and metformin. CONCLUSIONS: NAC was associated with improved clinical pregnancy but there was limited evidence that NAC improved live birth rates alone or in combination with clomiphene.  Given the quality of studies, these findings require further confirmation to establish the role of NAC in improving reproductive outcomes in women with PCOS.