Although vaccination against Streptococcus pneumoniae (S. pneumoniae) and Haemophilus influenzae type b (Hib) is recommended for immunocompromised patients, such as patients with B-cell chronic lymphocytic leukaemia (B-CLL), its protective effect is questionable. We studied antibody responses to pneumococcal polysaccharide vaccine (Pneumovax-23) and to conjugated H. influenzae type b-vaccine (Act-Hib) in 25 patients with B-CLL. After vaccination, the number of patients with antibody levels in the protective range against pneumococcal serotypes and H. influenzae b increased from 9 (38%) to 12 (50%) of 24 patients and from 8 (35%) to 11 (48%) of 23 patients, respectively. The patients with adequate antibody response to Pneumovax-23 and Act-Hib had significantly less advanced stages of B-CLL, higher gammaglobulin levels, total IgG-levels and IgG-subclasses 2 and 4 levels, and lower levels of soluble CD23. Consequently, vaccination with these vaccines should be given as soon as the diagnosis of B-CLL is made, early in the course of the disease with determination of post-vaccination antibody levels.