A lipiodol hysterosalpingogram was the routine test for tubal patency as recently as the 1970s. Observational studies, then randomised controlled trials, provided evidence of a fertility enhancing effect of lipiodol. It has been found to improve fertility for women with normal tubal patency, particularly where the woman has a history of endometriosis. Previous successful treatment for infertility with lipiodol is a marker of further successful treatment for infertility in a repeat procedure. Whilst lipiodol is probably effective at flushing debris that could hinder fertility from fallopian tubes, it also exerts immunobiological effects in pelvic peritoneum and on the endometrium that could be responsible for fertility enhancement. Effects of lipiodol on the endometrium that might be important at the time of the implantation window are a reduced expression of osteopontin and an increased number of uterine natural killer cells postlipiodol. The effect of lipiodol uterine bathing for women with endometriosis, repeat in vitro fertilisation (IVF) implantation failure and other reproductive disorders merits further investigation. Lipiodol presents a new, simple, low invasive, inexpensive treatment option for endometriosis‐related infertility and might have wider applications.