In the present study, the gamma delta T cell content of the tonsillar T cell population has been evaluated for the first time. Flow cytometric analysis showed that 1.56% of T cells in palatine tonsils obtained from patients with recurrent tonsillitis (n = 17) expressed the gamma delta T cell receptor. Next, the tissue distribution of these cells in palatine tonsil was examined immunohistologically. Gamma delta T cell receptor positive cells and CD3 positive cells were counted in the crypt epithelium, tonsillar epithelium on the free surface and in the interfollicular space (n = 29). The gamma delta T cell content of the whole T cell population in each of these regions was calculated and compared. It was demonstrated that T cells in the crypt epithelium contained more gamma delta T cell receptor bearing cells than did T cells infiltrating the tonsillar epithelium on the free surface. T cells in the interfollicular space included even fewer gamma delta T cells. The gamma delta T cell content of tonsillar T cells showed a gradual decrease with age in each region. Then, infiltration of gamma delta T cells in the crypt epithelium was compared among recurrent tonsillitis, hypertrophic tonsil and focus tonsil (PPP) specimens. Recurrent tonsillitis showed the highest gamma delta T cell content in T cells infiltrating the crypt epithelium. There was no remarkable infiltration of these cells in the crypt epithelium of focus tonsil. Furthermore, the gamma delta T cell population was isolated from tonsillar lymphocytes and stimulated with staphylococcal enterotoxin A (SEA), staphylococcal enterotoxin B (SEB) and toxic shock syndrome toxin-1 (TSST-1).(ABSTRACT TRUNCATED AT 250 WORDS)