Medical management of ectopic pregnancy with methotrexate, an antimetabolite of folic acid, is an important alternative to surgical treatment, as it ensures a similar outcome whilst being far less invasive. Ultrasound evaluation does not only facilitate an accurate diagnosis, but also helps to select patients most likely to benefit from methotrexate treatment, as opposed to those with a high likelihood of failure of medical management, who are thus eligible for primary surgical treatment. Ultrasound also allows to monitor the outcome of methotrexate therapy. This study is a review of literature regarding the management of ectopic pregnancy with methotrexate. Such ultrasound findings as the size of the ectopic mass, presence of fetal heart rate and free fluid have been confirmed as effective eligibility criteria for therapy with methotrexate. In the future, possibly also endometrial stripe thickness and the vascularity of the ectopic mass may be considered predictive of successful methotrexate therapy. The initial increase in size of the ectopic mass following methotrexate therapy confirms its effectiveness, and should not prompt concern.