Adhesion molecule CD11b/CD18 expressed by neutrophils (PMNs) participates in cell migration and phagocytosis of C3bi derivatized bacteria. It is this phagocytic function that eliminates some of the known periodontal pathogens in periodontal pockets. In patients with advanced periodontitis, homotypic aggregation of crevicular fluid PMNs (CF-PMNs) may occur due to overexpression of CD11b/CD18 and this may lead to ineffective elimination of periodontal pathogens. We have previously shown that CF-PMNs isolated from the periodontal pockets overexpress CD11b compared to PB-PMNs. This study tested the hypotheses that (1) overexpression of surface CD11b correlates with expression of CD11b mRNA in CF-PMNs isolated from advanced periodontitis subjects, and (2) the intrinsic capacity of CD11b mRNA upregulation by PB-PMNs from periodontitis patients differs from that of control subjects. CF-PMNs and peripheral blood PMNs (PB-PMNs) were isolated from 13 subjects with healthy gingiva (control group) and 13 subjects with advanced periodontitis (patient group). The surface expression of CD11b was determined by flow cytometry and CD11b mRNA was determined by extraction of mRNA and reverse transcription to cDNA followed by DNA amplification using primers to detect a segment of the cDNA which encodes CD11b. The results of this study confirm that the surface expression of CD11b on CF-PMNs is significantly higher in periodontitis subjects vs control subjects (p = 0.03), whereas surface CD11b expression on PB-PMNs does not differ significantly between groups (p = 0.06). The level of surface CD11b expression on CF-PMNs did not correlate with the amount of mRNA present in CF-PMNs in either group (p = 0.056, 0.07 for control and periodontitis patients, respectively). Most (9 of 13) individuals in the patient group expressed CD11b mRNA whereas very few control subjects (2 of 11) had CD11b mRNA in their CF-PMNs. This difference between groups was statistically significant (p = 0.004). The capacity to upregulate CD11b mRNA upon stimulation with fMLP and/or GM-CSF was highly variable and there was no statistical difference between the 2 groups.