Chronic lymphocytic leukemia (CLL) is one of the most common lymphoid malignancies in Western countries, but is infrequent in Asian populations. To verify the incidence of trisomy 8 in Chinese patients with CLL, fluorescence in situ hybridization (FISH) was used in 140 CLL patiens after routine chromosome analysis. Only two patients (1.4%) were found with trisomy 8, and the number of trisomy 8 cells was 8 and 10%, respectively. No other aberrations by "panel" probe FISH were found in these two patients. The chromosome karyotypes of two patients were 47,XY,+8[2]/49,XY,+14,þ20,+21[2]/46,XY[16] and 47,XX,+8[2]/46,XX[18], respectively. Neither of the patients' present signs of myelodysplastic or myeloproliferative disorder appeared on the bone marrow aspirates and peripheral blood smear. Our study demonstrates that trisomy 8 is rare in CLL, and its role in prognosis of CLL remains unkuown.