A case of pulmonary sarcoidosis and idiopathic CD4+ T lymphocytopenia is reported. Pneumocystis carinii was detected in the bronchoalveolar lavage fluid of a young homosexual man who was asymptomatic without any evidence of congenital or acquired immunodeficiency but with a low CD4+ cell count. A clinical and histological diagnosis of pulmonary sarcoidosis was made. During follow up the patient had oral candidiasis and a CD4+ cell count persistently below 300/microliters. This case is highly suggestive of concurrent pulmonary sarcoidosis and idiopathic CD4+ T lymphocytopenia.