Objectives: To define the involvement of CALM and AF10 fusion transcripts in primary leukaemias with t(10; 11). Methods: The AF10 and CALM fusion in five t(10; 11) leukemia samples were checked by reverse transcriptase-polymerase chain reaction (RT-PCR), and effects of CALM/AF10 antisense phosphorothioate oligodeoxynucleotides (AS PS-ODNs) on chemotherapy sensitivity and apoptosis of leukemia cells in vitro were observed. Results: Five different-sized AF10-CALM products and four different-sized CALM/AF10 products were detected by RT-PCR. The chemotherapy sensitivity of leukemic cells with t(10; 11) to drugs in vitro was lower than that of leukemic cells without t(10; 11). AS PS-ODNs increased the chemotherapy sensitivity and apoptotic rate. There were 4 cases positive at 5 (mol/L concentration, a11 cases positive at 10 (mol/L and 20 (mol/L concentration, P<0.01 vs only chemotherapeutic drugs (3 cases positive), and chemotherapeutic drugs ( S-PS-ODNs (10 (mol/L) (3 cases positive). After cells were treated with 10 (mol/L AS-PS-ODNs ( chemotherapeutic drugs for 48 h, 72 h, 96 h, the apoptotic indexes were 14.22 ( 2.86, 29.39 ( 3.57, and 41.26 ( 4.52, respectively. These were significantly higher than those of only chemotherapeutic drugs-treated cells and chemotherapeutic drugs ( S-PS-ODNs-treated cells at corresponding time (P<0.01). There was no difference between only drugs group and S-PS-ODNs group at corresponding time (P>0.05). Conclusion: The CALM and AF10 fusion transcripts are involved in the pathogenesis of haematological malignancies with t(10, 11), and is associated with a poor prognosis. AS-PS-ODNs might be useful in therapy of t(10, 11) leukemia.