The aim of study was to investigate the importance of chromosome aberration in differential diagnosis of eosinophilia and the chromosomal aberrations involved in patients with clonal eosinophilia. 65 cases of eosinophilia were collected and chromosome specimens of bone marrow cells were prepared by 24-hour culture, and G-banding technique was used for karyotyping. The results showed that out of 65 cases, chromosome 16 inversion was detected in 9 patients suspected as M(4Eo), and among the other 56 cases, 5 were detected with chromosomal aberrations (8.9%). Combining clinical, hematological and cytogenetical data, the 5 patients were diagnosed as acute myeloid leukemia with eosinophilia, chronic eosinophilic leukemia, 8p11 myeloproliferative syndrome, chronic myeloid leukemia in acute phase and acute myeloid leukemia-M(4Eo) respectively. The detected chromosomal aberrations were +14, t (5; 12) (q31; p13), t (8; 9) (p11; q32), t (9; 22) (q34; q11) and inv (16) (p13 q22). In conclusion, cytogenetical detection is very important in differential diagnosis of clonal eosinophilic disorders and chronic eosinophilic leukemia, which is suggested to be done routinely in clinic.