Aim:  To determine the best treatment for unexplained infertility. Methods:  A retrospective study was used to examine Japanese women with unexplained infertility that had undergone laparoscopy. The main outcome measure of the study was the rate of pregnancy after laparoscopy. Results:  One hundred and thirty-eight women diagnosed with unexplained infertility received laparoscopy and as a result 55 women had their diagnosis of unexplained infertility confirmed. There were no statistically significant differences between the women who became pregnant after laparoscopy in terms of duration of infertility, duration of treatment or age. The pregnancy rate of women with unexplained infertility was 56.4%, with 90% of these pregnancies achieved within the first 6 months. There were 64 women with minor endometriosis considered to be suffering from unexplained infertility before laparoscopy. The characteristics of the patients in the unexplained infertility group and in the minor endometriosis group were similar, but patients with minor endometriosis were found to have a lower pregnancy rate compared to those with unexplained infertility (35.9%vs 56.4%; P = 0.02). Conclusions:  The effective period after laparoscopy appears to be 6 months. Assisted reproductive technology should be considered after that time. Pregnancy rates were low in women with minor endometriosis compared with unexplained infertility. It is important to clarify the cause of infertility using laparoscopy. (Reprod Med Biol 2006; 5: 59-64).