CD38 identifies a surface molecule with multi-functional activity. Its prognostic importance in B-cell chronic lymphocytic leukemia (B-CLL) is currently under investigation in view of the fact that two different groups have recently indicated that CD38 expression could be an independent prognostic marker in B-CLL. We analyzed the clinico-biological features of 61 immunologically typical (CD5+CD23+) B-CLL patients stratified according to the CD38 expression. Twenty-two (36%) patients expressed CD38 in more than 30% of CD19-positive cells and were considered as CD38-positive B-CLL. Atypical morphology (p 0.02), peripheral blood lymphocytosis (p 0.01) and diffuse histopathologic bone marrow pattern (p 0.003) were findings found to be closely associated with CD38 expression. On the other hand, A and B Binet stages (p 0.02) and interstitial bone marrow involvement (p 0.005) were more represented in the CD38-negative B-CLL group. Trisomy 12 was detected more frequently in the CD38-positive B-CLL group, while 13q14 deletions mainly occurred in CD38-negative group (p 0.005). Finally, median survival of CD38-positive B-CLL patients was 90 months, while it was not reached at 180 months in CD38-negative patients. Taken together, our data strongly suggest that the evaluation of CD38 expression may identify two groups patients with B-CLL greatly differing in their clinico-biological features.