We conducted a study to localize and quantify the thromboxane B2 (TXB2) in human gingival tissue obtained from clinically healthy sites and patients with gingivitis and periodontitis. Human gingival samples were assayed for TXB2 by immunofluorescence on slides and enzyme-immunoassay (EIA). We found that concentrations of TXB2 in gingivitis sites are at mean 10-fold higher than in the healthy sites and histologically show a consistently intracytoplasmic staining with a significant increase in gingivitis. This argues in favour of a local production of TXB2. Concentrations of TXB2 at periodontitis sites are only 3-fold higher than in healthy sites and histologically show a stronger staining as for the gingivitis sections, with principally an extracellular localization. Thus, TXB2 could be released in large quantities in the crevicular fluid when the periodontitis stage has reached. These data suggest that the epithelial cells of the gingival tissue are involved in synthesis and secretion of TXB2, which occurred during the development of gingival inflammation.