Abstract： Background Under conventional cytogenetic (CC) analysis, only 30%-50% of B cell chronic lymphocytic leukemia (B-CLL) cases show clonal aberrations. Using fluorescence in situ hybridization (FISH), the percentage of patients with abnormalities rises to almost 80%, among them, the most frequent abnormalities were 13q14, 11q22, p53 deletions and trisomy 12. The aim of this study was to explore the incidence of cytogenetic changes in Chinese patients with B-CLL.Methods We used FISH methods to detect the cytogenetic features in 275 cases of B-CLL from 48 hospitals. The correlation between FISH abnormalities and clinical characteristics such as age, gender, white blood cell count,peripheral hemoglobin (Hb) level, peripheral platelet count (PLT), lactate dehydrogenase (LDH) level, Rai stage, Binet stage, and overall survival was analyzed, and the relationship between them and overall survival was also analyzed to evaluate their prognostic implications.Results Of the 275 patients, genetic aberrations were found in 77.8% using FISH. The frequencies of abnormalities were as follows: 13q deletion (56.4%), trisomy 12 (34.5%), p53 deletion (33.5%) and 11q22 deletion (30.5%). It was obvious that the patients with p53 deletion had lower level of Hb (P=0.001) and PLT (P=0.003) when compared to patients without p53 deletion. Significant differences were obtained in the distribution of p53 deletion according to Rai and Binet classification systems (P=0.016 and 0.008 respectively). Significant differences were also observed when the overall survival was correlated with p53 deletion (P=0.043), Rai stage (P=0.006), Binet stage (P=0.013), Hb level (P=0.004) and PLT level (P=0.010).Conclusions Chinese CLL patients have the similar frequencies of del(13q), trisomy 12, del(11q) and a higher frequency of del(17p) when compared to literatures. Del(17p) is associated with advanced stage and low levels of Hb and PLT. Patients with p53 deletion, or advanced stage probably have poor survival in China.