The translocation t(8;21)(q22;q22) occurs in 6 to 12 percent of patients with AML, and usually predicts a good response to chemotherapy with a high remission rate and a relatively long median survival. The influence of additional chromosome aberrations on the clinical outcome of patients with t(8;21) is unclear. We analyzed 51 cases of acute myeloid leukemia carrying a translocation t(8;21)(q22;q22); 23 female and 28 male patients. The complete remission rate was 92 percent and median overall survival was 52.4 months. The median overall survival of female patients was significantly worse than of male patients (37.2 months vs not reached, P = 0.025). Additional chromosome aberrations were detected in 41 patients at diagnosis (80 percent), 31 (61 percent) had lost a sex chromosome, seven (14 percent) showed a partial deletion of the long arm of chromosome 9 and in three patients (6 percent) a gain of chromosome 8 was observed. Whereas the loss of a sex chromosome had no influence on prognosis, a partial deletion of the long arm of chromosome 9 was an unfavorable prognostic factor. The median overall survival of the seven patients with del(9q) was only 12.5 months and thus significantly shorter than in patients with only t(8;21) or with t(8;21) and additional sex chromosome loss (median survival not reached: P = 0.0010).