CD38-expression profiles of B-CLL cells and T cells significantly correlate with time from diagnosis to first treatment in male patients with B-CLL. Female (A) and male (B) patients were stratified into 4 risk groups according to the expression levels of CD38 in B-CLL cells and T cells (group I: no CD38 risk, ie, CD38 expression in < 50% of T cells and < 30% of B-CLL cells; group II: ≥ 50% CD38⁺ T cells; group III: ≥ 30% CD38⁺ B-CLL cells; group IV: ≥ 50% CD38⁺ T cells and ≥ 30% CD38⁺ B-CLL cells). Kaplan-Meier analysis of treatment-free survival revealed CD38⁺ B-CLL cells as a prognostic factor both in female and male patients. In contrast, the presence of at least 50% CD38⁺ T cells predicted for significantly shorter treatment-free survival in male but not in female patients. Numbers of patients in the respective subgroups are indicated. P values for comparison of risk groups using the log-rank test are presented.