Background: The oviduct plays a major role in fertility by facilitating the movement of gametes to promote fertilization and passage of the embryo for implantation. In the present study, we compared the distribution of nerve fibers in the ampulla of the oviduct tube in patients who presented with and without ectopic pregnancy (EP). Our aim was to acquire a better understanding of the pathologies underlying EP. Methods: We recruited 25 patients with EP (representing group A) and 25 patients who underwent hysterectomy for benign gynecological diseases (representing group B). None of the recruited women had a previous history of induced abortion. We acquired the oviduct ampulla from each patient in the two groups and used immunohistochemistry to detect S100 and protein gene product 9.5 (PGP9.5) and reveal abnormal distributions of nerve fibers within the fallopian tubes. Results: There was no statistical difference between the two groups in terms of the proportion of S100- and PGP9.5-immunoreactive nerve fibers in the mucosal, muscular and serosal layers of the oviduct ampulla. However, the proportions of S100- and PGP9.5-immunoreactive nerve fibers were reduced in the mucosal, muscular and serosal layers of the oviduct ampulla in women with EP when compared to women without EP. Conclusions: The reduced density of nerve fibers in the endometrial and muscular layer of the ampulla of the fallopian tube, as detected by PGP9.5 and S100, may play a significant role in the pathologies underlying ectopic pregnancy.