Diversity of outer membrane protein profiles of nontypable Haemophilus influenzae from children from Papua New Guinea and the Philippines. We determined capsular serotypes and, with use of SDS-PAGE, patterns of outer membrane proteins (OMP) of Haemophilus influenzae isolates from specimens of blood, lung, or CSF from children with acute respiratory tract infections or meningitis who were hospitalized in Papua New Guinea or the Philippines. Among 72 isolates from Papua New Guinea, 72% were type b, 14% were other encapsulated serotypes, and 14% were nontypable. The respective frequencies among 43 isolates from the Philippines were 56%, 7%, and 37%. The type b isolates could be subdivided into at least eight outer membrane subtypes, most of which have been described previously. In contrast, OMP profiles of the nontypable H. influenzae isolates from children in both countries were highly heterogeneous. These results differ markedly from those previously found for isolates from children with acute respiratory tract infections in Pakistan, for which encapsulated H. influenzae strains other than serotype b were not observed; 95% of type b isolates were of a single OMP subtype; and nontypable isolates showed evidence of clonal restriction. Candidate vaccines for use in developing countries as protection against disease caused by H. influenzae will need to include both capsular and noncapsular antigens and investigators must take into consideration regional differences among strains. 