To investigate the influence of smoking on the aging immune system, the following parameters were determined in elderly smokers and non-smokers: presence of emphysema; absolute number of leucocytes, lymphocytes, T cells and B cells bearing membrane-bound IgG; serum IgG, IgA, IgM levels, occurrence of rheumatoid and antinuclear factors, and natural antibody level (against different bacteria). Ultrastructural disorders in lymphocytes were also investigated. The number of leucocytes, the levels of serum IgA, and the prevalence of autoantibodies were higher, and the natural antibody level was lower in smokers than in non-smokers. Giant mitochondria and cytoplasmic disorders were found more frequently in smokers than in non-smokers, and in an even higher rate in smokers with emphysema. These findings suggest that smoking may accelerate the appearance of age-dependent (especially disease-related) immunological changes.