Background : The physiological regulation of the ovary is a complicated process ; the growth factor, steroid hormones, gonadotropins, and cytokines all take part. Inflammatory cytokines are found in many compartments of the ovary, such as the follicles. The ovarian tissue produces them in addition to the macrophages. In this study, we aimed to compare the level of serum and follicular fluid IL-1Beta (IL-1β) for different groups of infertile patients, comparing the ICSI outcome between sub-fertile couples due to different causes. The results of this study IL-1β was significantly higher in the patients with unexplained subfertility (p-value < 0.05), no significant difference was found in the ICSI outcome between patients with different causes of subfertility. The lowest pregnancy rate was found in patients with unexplained subfertility, but the difference is insignificant. In conclusion, immunity plays a role in unexplained subfertility as patients with unexplained subfertility have a significantly higher serum level IL-1β than the other causes of subfertility. However, IL-1β does not affect ICSI outcome. Therefore, the ICSI outcome is not affected by the cause of subfertility. J. Med. Invest. 69 : 180-184, August, 2022