We previously tested a less toxic CAG regimen consisting of low-dose cytarabine, aclarubicin and granulocyte-colony stimulating factor for the treatment of patients with relapsed or refractory myeloid malignancies or elderly patients with untreated ones, obtaining a satisfactory complete remission rate of 62%. Gemtuzumab ozogamicin, an anti-CD33 monoclonal antibody conjugated to calicheamicin, has recently been approved as a single agent in Japan for the treatment of relapsed/refractory CD33-positive acute myelogenous leukemia (9 mg/m(2) on days1 and 15). Complete remission rate was reported as 30% in a phase 2 trial in Japan. In this study, effectiveness and safety of combining dose-attenuated gemtuzumab ozogamicin (3 mg/m(2) on day5) and original CAG regimen were assessed in nine patients with relapsed/refractory CD33-positive acute myelogenous leukemia and a median age of 70 years. Rate of complete remission with or without platelet recovery was 44% (4/9). The median duration of complete remission and overall survival were 5.5 and 16 months, respectively. Reversible myelosuppression and liver toxicity were the main adverse events, but no regimen-related death was recorded. Although only a small number of cases were included in this preliminary study, this CAG-GO regimen was found to be feasible and useful even in high-risk relapsed or refractory patients.