Objective: Evaluate the effectiveness of treatment low risk of Gestational Trophoblastic Diseases by 15mg methotrexate and side effects at National Obstetric and Gynecological Hospital (2003-2005). Methods: The descriptive study and retrospective. Results: The cure rate by 15mg methotrexate was 92,5 percent, the failure rate was 7,5 percent. The cure rate in choriocarcinoma was 97 percent, invasive mole was 89,2 percent. The rate of mouth ulcers 10,5 percent, the rate of leucopenia 10,5 percent, the rate of hepatitis 11,9 percent. Conclusion: The results treatment low risk of Gestational Trophoblastic Diseases by 15mg methotrexate was verry high and low side effects.