Objective: Evaluate the effectiveness of treatment low risk of Gestational Trophoblastic Diseases by 50mg methotrexate and side effects at National Obstetric and Gynecological Hospital 2007-2009. Methods: The descriptive study and retrospective. Results: The cure rate by 50mg methotrexate was 95,8 percent, the failure rate was 4,2 percent. The cure rate in choriocarcinoma was 100 percent, invasive mole was 92,7 percent. The rate of mouth ulcers 1,4 percent, the rate of leucopenia 1,4 percent, the rate of hepatitis 2,8 percent. Conclusion: The results treatment low risk of Gestational Trophoblastic Diseases by 50mg methotrexate was verry high and low side effects.