CD38-expression profiles of B-CLL cells (CD19⁺CD5⁺) and T cells (CD19^–CD5⁺) as detected by 3-color flow cytometry. Fresh blood samples were incubated with a mixture of fluorescence-labeled anti-CD19, anti-CD5, and anti-CD38 mabs for 15 minutes followed by lysis of red blood cells with a FACS lysing solution. CD19⁺CD5⁺ cells (B-CLL) and CD19^–CD5⁺ cells (T cells) were analyzed for CD38 expression. Representative results from a patient with CD38 low risk (< 30% CD38⁺ B-CLL cells, < 50% CD38⁺ T cells, left row) and CD38 high risk (≥ 30% CD38⁺ B-CLL cells, ≥ 50% CD38⁺ T cells, right row) are presented.