Objective The progression of myelodysplastic syndrome to acute myeloid leukemia (MDS/AML) is generally incurable and its prognosis is extremely poor. It is important to determine the predictive factors of response and survival in diseases treated with chemotherapy. Methods Twenty-nine patients who had been diagnosed of MDS/AML and had undergone chemotherapy between April 2001 and March 2008 were retrospectively analyzed. Results Of the 29 patients, 21 patients had an abnormal karyotype. Among them, 13 had complex type abnormalities and/or monosomy 7. Twenty-four patients were administered a low-dose AraC containing regimen and 5 received an AML-like regimen as the initial chemotherapy. The responses were CR4/PR2/NR23. The response rate (RR) in the patients with a normal karyotype was significantly better than in those with an abnormal karyotype (62.5% vs. 4.8%, p=0.003). Univariate analyses showed that the hemoglobin level and cytogenetic abnormalities were factors that contributed to the overall survival. Conclusion In MDS/AML, patients with a normal karyotype tended to have a better response to chemotherapy. The hemoglobin level and cytogenetic abnormalities were significant factors affecting the overall survival.