T cells expressing CD57 (a natural killer cell marker) with interferon-γ (IFN-γ) producing capacity increase under various conditions. CD57+ T cells are also present in the bronchoalveolar lavage fluid (BALF) of sarcoidosis, and several phenotypical and functional analyses of these cells have been reported. In the present study, BALF T cells obtained from 52 patients with sarcoidosis were classified further into CD4+CD57+ T cells, CD4+CD57– T cells, CD8+CD57+ T cells and CD8+CD57– T cells and their phenotypes and functional characteristics were assessed. Substantial proportions of these T cell subsets expressed natural killer cell markers CD161 and CD122. The biased expansion of Vβ2 T cells was observed in both CD4+CD57+ T cells and CD4+CD57– T cells in BALF from most patients, while the expansion of other Vβ T cells was also observed in some patients. Unexpectedly, the biased expansion of certain Vβ T cells was also seen in either CD8+CD57+ T cells or CD8+CD57– T cells, while the expanded Vβ T cells in CD8+ T cells differed substantially among individuals. BALF T cells showed a remarkably lower T cell receptor (TCR) intensity than that of peripheral blood T cells. Both CD8+ T cell subsets in BALF of sarcoidosis expressed the intracellular perforin/granzyme B, while all four subsets expressed intracellular IFN-γ after in vitro activation, and CD4+ T cells, especially CD4+CD57+ T cells, expressed tumour necrosis factor-α. These findings indicate that CD57+ T cells as well as CD57– T cells in the BALF are phenotypically and functionally different from peripheral blood T cells and may play an important role in the Th1 dominant state and inflammation in pulmonary sarcoidosis.