The frequency of CMV-specific CD4⁺ T cells in B-CLL patients is increased in advanced disease. The frequency of CMV-specific CD4⁺ T cells was determined by IFNγ production and grouped according to the Binet stage of disease. CMV-specific CD4⁺ T cells represented 8.2% of the CD4⁺ T-cell pool in patients with stage A disease (n = 29) compared with 15.2% in patients at Binet stages B and C (n = 16).