AML with inv(3)/t(3;3) are generally considered of having a poor prognosis. For further insight in this rare entity the outcome of 65 inv(3)/t(3;3) positive AML cases were examined with special emphasis o n patient a nd disease related factors at diagnosis. Survival data were available from 35 patients. A hematological CR was achieved in 16/35 patients (46%). Eight patients (50%) relapsed. The median duration of remission was 177 days. Probability of OS was 23% at 2 years. Advanced age and high initial WBC count were associated with shorter OS (p = 0.021 and p = 0.005, respectively). Loss of chromosome 7 was the most frequent additional aberration (n = 34; 52%), followed complex aberrant aberrations (n = 5). Cases with monosomy 7 or the presence of FLT3-length mutations (FLT3-LM)--detected in 13% of cases--were not associated with an even more inferior outcome. Allogeneic stem cell translplantation, performed in 12 cases, resulted in a probability of OS of 62% at 2 years. Our data (1) confirm that inv(3)/t(3;3) AML has a poor prognosis (2) show that age and initial WBC are risk factors for prognosis; (3) suggest that this group may benefit from allogeneic stem cell transplantation.