Gamma delta T cells have been implicated as playing a role in inflammatory and autoimmune conditions. In this study, a biotin-streptavidin peroxidase technique was used to determine the presence of T cells expressing alpha beta and gamma delta T cell receptors (TCR) in the inflammatory infiltrates of gingival tissue sections from gingivitis and adult periodontitis patients. The lesions were graded 1+ to 3+ according to the size of the infiltrate. alpha beta+ T cells predominated in all infiltrates with no differences in the mean percent (20 to 30%) according to size of lesion or to clinical status. A mean percent gamma delta T cells of 0.42 +/- 0.11 and 0.91 +/- 0.42 was demonstrated in 1+ infiltrates of gingivitis and adult periodontitis sections respectively. Although the mean percent gamma delta T cells increased in both gingivitis (2.09 +/- 0.54) and adult periodontitis sections (2.25 +/- 0.35) with increasing size of infiltrate, this was not statistically significant. However, when the mean proportion of gamma delta T cells of the total TCR bearing cells was determined, there was a significant 3 to 4 fold increase in adult periodontitis sections from 3.09 +/- 1.35 in 1+ lesions to 11.90 +/- 2.94 and 8.81 +/- 1.45 in 2+ and 3+ lesions respectively. A similar increase of the same magnitude occurred in gingivitis sections from 2.82 +/- 0.74 in 1+ lesions to 11.12 +/- 4.13 in 2+ lesions, but this was not significant (P = 0.055). There was no correlation between the increase in the proportion of gamma delta T cells and the T:B cell ratio or the CD4:CD8 ratio in individual lesions.(ABSTRACT TRUNCATED AT 250 WORDS)