Antibody response to 23-valent pneumococcal vaccine was assessed in 350 subjects (131 men, 219 women) aged 65-91 years. IgG antibodies to pneumococcal serotypes 4, 6B, 9V, 14, 19F, and 23F were measured by EIA after blocking of antibodies to cell wall polysaccharide. Antibody concentrations in both pre- and postvaccination sera (mean interval, 35 days) were higher in elderly men than women; in the women, the concentrations decreased significantly with increasing age, but not in the men. Antibody fold increases were good in the elderly, including those > or = 85 years old. The overall percentage of the elderly with antibody concentrations > 1 microgram/mL to the 6 antigens increased by vaccination from 61% to 87%, but in the women > or = 85 years old, only to 75%. Antibody response to 23-valent pneumococcal vaccine was satisfactory in the elderly.