Introduction: Assisted reproductive technology is used routinely for treatment of infertile spouses. Previous studies reported conflicting results regarding effect of progesterone rise at the HCG injection day. The aim of current study is to evaluate the effects of mid cycle progesterone levels in IUI cycles. Methods: In this analytical cross-sectional study, the outcome of treatment in 200 IUI cycles were evaluated. Patients’ demographic findings, progesterone level at the day of HCG injection, number of follicles >16 mm, endometrial thickness and clinical pregnancy rate were recorded. For better evaluation, progesterone levels were divided to <0.5, 0.5-1.5 and >1.5 ng/dl. Results: Patients’ mean age was 29.70±4.38 years. The progesterone levels of <0.5, 0.5-1.5 and >1.5 ng/dl was detected in 24.5%, 56% and 19.5% of patients, respectively. The rate of clinical pregnancy was 27.5%. Cases with positive pregnancy had significantly lower progesterone levels (0.88±0.31 vs.1.11±0.80, p=0.04). The highest pregnancy rate was in progesterone levels 0.5-1.5 compared to levels <0.5 and >1.5 ng/dl (42% vs. 12.2% vs. 5.2%, p<0.001). There was no significant correlation between progesterone levels with endometrial thickness (r=-0.130, p=0.06) and number of follicles >16 mm(r=0.02, p=0.77). Conclusion: The results of current study showed that the increase in progesterone levels at the day of HCG injection accompanies with lower pregnancy rate. However, this increase has no correlation with number of mature follicles and endometrial thickness.