A case of severe dyspnea, hypercalcemia and renal failure secondary to sarcoidosis is reported. The clinical diagnosis of sarcoidosis in a 48-year-old man was confirmed by histology and cytology. Transiently decreased numbers of CD4+ T cells (282/microliter) indicated impaired immunity in the absence of HIV-infection during the acute phase of the disease. Surprisingly, numerous "trophozoites" of Pneumocystis carinii were detected by immunofluorescence staining and PCR in the bronchoalveolar fluid indicating infection or colonization of the lungs. Corticosteroid therapy was administered together with trimethoprim-sulfamethoxazole and rapidly reduced elevated serum calcium and creatinine concentrations. Since airborne person-to-person transmission of P. carinii to susceptible individuals might be possible, patients with sarcoidosis could be a previously unrecognized reservoir for P. carinii distribution in hospitals and in the community at large.