In humans, infection with Bordetella pertussis is considered to be localized to an epithelial surface. However, an intracellular state in cultured cells and in the macrophages of infected animals has been shown. By using indirect immunofluorescence with a monoclonal antibody, it was found that 3 of 20 bronchoalveolar lavage specimens from children with human immunodeficiency virus infection had B. pertussis associated with pulmonary alveolar macrophages. None of the cultures from the patients grew B. pertussis. The B. pertussis appeared to be intracellular.