The aim of this study was to evaluate the efficacy and toxicity of EMA/CO (etoposide, methotrexate, actinomycin D, cyclophosphamide, vincristine) regimen for the treatment of high-risk gestational trophoblastic neoplasia (GTN). Thirty-three patients with high-risk GTN, scored according to World Health Organization, received 159 EMA/CO treatment cycles between 1994 and 2004. Twenty-three patients were treated primarily with EMA/CO, and 10 patients were treated secondarily after failure of single agent or MAC (methotrexate, actinomycin D, cyclophosphamide, or clorambucile) III chemotherapy. Adjuvant surgery and radiotherapy were used in selected patients. Survival, response, and toxicity were analyzed retrospectively. The overall survival rate was 90.9% (30/33). Survival rates were 91.3% (21/23) for primary treatment and 90% (9/10) for secondary treatment. Six (18.2%) of 33 patients had drug resistance. Four of them underwent surgery for adjuvant therapy. Three of these patients with drug resistance died. Survival and complete response to EMA/CO were influenced by liver metastasis, antecedent pregnancy, and histopathologic diagnosis of choriocarcinoma. Survival rate was also affected by blood group. The treatment was well tolerated. The most severe toxicity was grade 3-4 leukopenia that occurred in 24.3% (8/33) of patients and 6.9% (11/159) of treatment cycles. Febrile neutropenia occurred in one patient (3%). EMA/CO regimen is highly effective for treatment of high-risk GTN. Its toxicity is well tolerated.