To investigate the cytogenetic and clinical characteristics in patients with abnormalities at the short arm of chromosome 12, chromosome specimens were prepared by 24-hour culture of bone marrow cells and undergone karyotype analysis by G-banding technique. The results showed that aberration at the short arm of chromosome 12 were detected in 16 cases with 12p balanced translocation, in 10 cases with 12p deletion, 6 cases with 12p addition, and in 1 case with inversion 12. By complex karyotype classification, 12p translocation included 6 simple aberrations, 6 complex aberrations, and 4 highly complex aberrations; while 12p deletion were mainly composed of highly complexity of aberration. Patients consisted of acute leukemia, myelodysplastic syndrome, chronic myelogenous leukemia and so on. Clinical follow-up data were available in 14 patients, in which 8 cases of acute leukemia were treated with conventional chemotherapy only. Three of them attained complete remission, and the median survival time in 8 patients was 5.5 months. In conclusion, the aberrations at short arm of chromosome 12 were involved in a broad spectrum of haematological malignancies, and the karyotypes showed most complexity of aberration with low remission rate and short survival in clinic.