Streptococcus pneumoniae is one of the major invasive pathogens in childhood. The increasing worldwide prevalence of penicillin-resistant strains makes management of invasive infections difficult and underscores the need for effective vaccines. Currently available vaccines are of limited value in the pediatric age group. Trials are taking place to evaluate conjugated pneumococcal vaccines and in view of this it is important to establish local epidemiology of pneumococcal disease. The aims of this population-based study were to review all of the cases of invasive pneumococcal disease occurring during a 9-year period (1984 to 1992) in Auckland, New Zealand. Through the use of laboratory records and hospital discharge codes, 413 isolates from 407 patients were found. Age-specific incidence for all invasive disease was 22.0/100,000 for children less than 15 years old but 56.0/100,000 for children less than 5 years old (chi 2 Yates corrected 18.20; P = 0.001). Two-thirds were less than 2 years old. The rates were higher in Maori and Pacific Island children than in Caucasian children. A total of 70 isolates from 68 patients with meningitis occurred. The majority were less than 5 years old (incidence of meningitis was 10.0/100,000) and 84% were less than 2 years old. The overall mortality from meningitis was 4.3%. Of the 129 isolates serogrouped or serotyped, 14, 6 and 19 accounted for 23%, 16% and 16%, respectively, of cases. Although 98% of serotypes identified would be covered by the currently available 23-valent vaccine, two-thirds of the children affected by these isolates would be unprotected because of poor immunogenicity of polysaccharide vaccines in children less than 2 years old.