In granulomatous inflammatory lung diseases such as sarcoidosis, the balance of cytokine production by activated T cells in the lungs may influence clinical disease outcome. To investigate the potential of T lymphocytes to produce cytokines and contribute to this process, T cells from bronchoalveolar lavage (BAL) and PB from 19 patients with active lung disease were stimulated, stained, and analysed by flow cytometry for intracellular production of cytokines and expression of the activation marker CD69. Higher proportions of BAL cells expressed CD69 compared with PB, in the absence of in vitro stimulation. The expression of IFN-gamma was similar in unstimulated BAL and PB T cells, and there was no association between the expression of CD69 and IFN-gamma. Following stimulation, there were increased numbers of IFN-gamma(+) T cells. A similar trend was found with IL-2(+) T cells, but there were lower levels of IL-4(+) T cells in BAL compared with PB, and similar levels of IL-10(+) T cells. The presence of activated T lymphocytes in BAL samples from patients with sarcoidosis, with the potential to produce Th1 type 1 cytokines may contribute to the inflammatory processes in this granulomatous lung disease. The use of intracellular flow cytometry to investigate cytokine production by BAL T cells could help to indicate potential targets for future therapy.