The objective of this study was to assess the prevalence of beta-lactamase production in Haemophilus influenzae clinical isolates obtained throughout Latin America and the West Indies in 1998-1999. Isolates were collected from 15 centres (seven countries), identified by standard methods and grouped by patient age. The overall prevalence of beta-lactamase production was 17.8% (270/1513 isolates). The prevalence of beta-lactamase positive strains varied between countries, with the highest prevalence detected in Panama (23.4%, 29/124) and the lowest in the West Indies (10.5%, 4/38). beta-Lactamase-positive strains were more frequently isolated from children aged < or =3 years (22.0%) and from adults aged > or =65 years (26.5%). The high prevalence of beta-lactamase production found should be considered when choosing empirical antibiotic therapy where H. influenzae is suspected.