Previous studies on the relationship between activated BAL T lymphocytes and clinical features in sarcoidosis revealed controversial results. We determined lavage lymphocytes, T lymphocytes, activated T lymphocytes, helper, suppressor and natural killer cells in 50 patients with pulmonary sarcoidosis and compared the results with clinical findings, serum angiotensin converting enzyme (ACE), the radiological pattern and lung function data (vital capacity [VC], total lung capacity [TLC], FEV1, transfer coefficient KCO and arterial-alveolar oxygen difference [AaDO2] during exercise). Patients with erythema nodosum (n = 7) showed a lower proportion of activated T lymphocytes (p < 0.05) and lymphocytes (p < 0.01) than the other patients. There was a significant correlation between activated T lymphocytes and AaDO2 during exercise (r = 0.49, p < 0.001), and an inverse correlation was seen between activated T lymphocytes and VC or TLC (r = -0.35 and r = -0.36, p < 0.01). We conclude that the percentage of activated BAL T cells may be related to the degree of parenchymal involvement as expressed by functional disturbance.