BACKGROUND: Ectopic pregnancy is the implantation of fertilized ovum on any tissue other than the endometrial lining of the uterus. OBJECTIVE: To evaluate the effectiveness and safeness of methotrexate in the treatment of unruptured ectopic pregnancy. MATERIALS AND METHODS: From January 2000 to October 2002 five patients were diagnosed with unruptured ectopic pregnancy in Hospital Juarez de Mexico. The inclusion criteria were: hemodynamic stability, gestational sac of < 40 mm, serum beta-hCG concentration < 15,000 mIU/L and future fertility desire. Systemic methotrexate was administered as an intramuscular injection of 50 mg. Evaluation was based on transvaginal ultrasonography, beta-hCG levels and hysterosalpingography. RESULTS: Five patients with unruptured ectopic pregnancy were treated with methotrexate. Successful rate, after one or two injections, was 100% (5 patients). The size of ectopic pregnancy as estimated by ultrasonographic was 33.33 mm. Negligible plasma beta-hCG values were reached 45.6 +/- 19.85 days after the time of treatment. Ultrasonographic scanning demonstrated progressive disorganization and the gestational sac disappeared at 134 days after treatment. There were no adverse effects from the chemotherapy. In 3 of 4 women who underwent hysterosalpingography following treatment, patency of the affected tube was observed. Three women experienced an intrauterine pregnancy spontaneously in the methotrexate group. CONCLUSIONS: Systemic methotrexate treatment is safety and effective in the treatment of unruptured ectopic pregnancy, for woman with future desire of fertility and if it has unruptured, conservative treatment using methotrexate is an excellent choice.