We have reported that lactoferrin, a 77-kDa iron-binding glycoprotein found in secondary neutrophil granules, provides a useful marker of fecal leukocytes in fecal specimens from patients with inflammatory diarrhea (R. L. Guerrant, V. Araujo, E. Soares, K. Kotloff, A. A. M. Lima, W. H. Cooper, and A. G. Lee, J. Clin. Microbiol. 30:1238-1242, 1992). In order to determine the usefulness of this marker of neutrophilic inflammation in different body fluids, we examined blood, gingival swabs, sputum, and saliva using antilactoferrin antibodies (lactoferrin latex agglutination [LFLA]). LFLA titers in whole blood samples were < or = 1:4 in all eight samples from patients with neutropenia (absolute neutrophil count [ANC] = < 150 polymorphonuclear cells [PMNs] per microliter), < or = 1:8 in samples from 13 individuals with moderate leukocyte counts (ANC = 150 to 8,000), and 1:8 to 1:32 in samples from six patients with neutrophilia (ANC > 8,000). While the overlap precludes a useful role in the identification of neutropenia, these data confirm that lactoferrin titers of > 1:100 indeed indicate inflammation in fluid specimens. On quantitative elution of lactoferrin from gingival swabs, all 7 patients with dental plaque had titers of 1:200 to 1:400; 9 of 12 patients with clinical gingivitis had LFLA titers of 1:200 to 1:1,600, while all 7 individuals with healthy gums and teeth and 4 edentulous patients had LFLA titers of < or = 1:100. Eight purulent sputum samples had titers of > or = 1:400 (7 were 1:1,600) while 11 normal saliva samples showed titers of < or = 1:100. Lactoferrin titers in sputum, gingival swabs, and whole blood correlate with the presence of neutrophils or inflammation in these specimens and may offer a convenient rapid test for inflammatory processes.