To explore the ZAP-70 expression in chronic lymphocytic leukaemia (CLL) and its relationship with other prognostic factors, the expressions of ZAP-70 protein and CD38 in bone marrow or peripheral blood of 24 patients with B-CLL were determined by four-color flow cytometry. The results showed that ZAP-70 was positively expressed in 37.5% of all B-CLL patients, 20% (3/15) patients in Binet A stage, and 66.7% in Binet B + C. The expression of ZAP-70 had significant difference between Binet A and Binet B + C (P < 0.05). CD38 was expressed in 29.1% of B-CLL patients and 3 out of these cases were in stage A, 2 out of 3 cases in stage A co-expressed CD38 and ZAP-70. The expression of CD38 had no significant difference between Binet A and Binet B + C stage (P > 0.05). ZAP-70+ and CD38+ were both expressed in 83.3% of B-CLL patients (P < 0.05). It is concluded that ZAP-70 protein can be routinely measured by flow cytometry in the laboratory. High expression of ZAP-70 is correlated with other prognostic factors such as clinic stage, chromosome abnormalities and CD38 in B-CLL.