OBJECTIVE: To discuss the possible role of abnormal embryo migration as a cause of ectopic pregnancy during IVF with hydrosalpinges. DESIGN: Case report. SETTING: University-based reproductive endocrinology and fertility clinic. PATIENT(S): A patient presenting with a tubal ectopic pregnancy after spontaneous conception in a preexisting hydrosalpinx. INTERVENTION(S): Laparoscopic salpingectomy. MAIN OUTCOME MEASURE(S): Ultrasound and operative findings. RESULT(S): Case demonstration of abnormal embryo migration into a surgically documented preexisting hydrosalpinx during a spontaneous conception. CONCLUSION(S): The mechanism of increased tubal ectopic pregnancy rates during IVF with hydrosalpinges remains unexplained. This case supports abnormal embryo migration due to the hydrosalpinx as a contributing factor.