Introduction: C-reactive protein (CRP) is a sensitive marker of endothelial activation and inflammation process. The association between an inflammatory state and CRP has prompted research on changes in CRP levels in assisted reproductive technique (ART) cycles. The aim of this survey was to assess CRP levels during IVF stimulation and to correlate them with IVF success.Materials and Methods: Eighty women, who underwent IVF treatment, were prospectively studied in Fatemiyeh University Hospital, Hamadan University of Medial Sciences during 2007. Women excluded with an autoimmune diseases, recent history of surgical, trauma and infection. Levels of serum CRP were evaluated on the following days: oocyte retrieval, embryo transfer and 12 days after embryo transfer Women with positive b-hCG levels (>10000 IU) had ongoing pregnancies, confirmed by ultrasound scans served as conceived or successful IVF group.Results: Seventeen (21%) patients had successful IVF. In comparison to non-pregnant or IVF failure group, CRP levels were significantly lower in successful IVF group. CRP levels were 2.48±2.18 mg/l on oocyte retrieval day, 2.50±1.45 mg/l on embryo transfer day and 1.94±1.39 mg/l 12 days after embryo transfer (p<0.001) in successful IVF group. The CRP levels were not significantly different in each group according to day of sample retrieval (p>0.05).Conclusion: In women treated successfully by IVF, the CRP concentrations were significantly lower than the non-pregnant group