T-cell function directly influences several B-cell functions. The effect of T-cell subgroups on B-cell function (DNA synthesis) was evaluated for controls and patients with B-cell type of CLL. Control and CLL intact T cells, T cells with receptors for IgG (T gamma), and T cells without Fc receptors at isolation (T non-gamma) were admixed with control B cells. Two predominant differences between control and CLL T cells were observed. First, CLL T gamma cells were excessively effective at suppressing B-cell DNA synthesis, and secondly, control T non-gamma cells were more efficient than CLL T non-gamma at promoting control B-cell DNA synthesis. While it is unclear whether the qualitative and quantitative T-cell abnormalities are part of the CLL disease process, it is possible that excessive T gamma cell numbers and function may reflect an appropriate immune response to a malignant B-cell clone.