Sarcoidosis, a systemic granulomatous disease of undetermined etiology, is characterized by a variable clinical presentation and course. During the past decade, advances have been made in the study of sarcoidosis. The multicenter ACCESS (A Case Control Etiologic Study of Sarcoidosis) trial recruited > 700 subjects with newly diagnosed sarcoidosis and matched control subjects. Investigators were unable to identify a single cause of sarcoidosis, but ACCESS paved the way for subsequent etiologic studies. The Mycobacterium tuberculosis catalase-peroxidase protein has been identified as a potential sarcoidosis antigen. Genetic aspects of the disease have been elucidated further. Genome-wide scans have identified candidate genes. Gene expression analyses have defined cytokine dysregulation in sarcoidosis more clearly. Although the criteria for diagnosis have not changed, sarcoidosis remains a diagnosis of exclusion best supported by a tissue biopsy specimen that demonstrates noncaseating granulomas in a patient with compatible clinical and radiologic features of the disease. Endobronchial ultrasound-guided transbronchial needle aspiration of mediastinal lymph nodes has facilitated diagnosis, often eliminating the need for more invasive procedures, such as mediastinoscopy. PET scanning has proven valuable in locating occult sites of active disease. Currently, no reliable prognostic biomarkers have been identified. The tumor necrosis factor inhibitors, a relatively new class of agents, have been used in patients with refractory disease. It is unclear whether phosphodiesterase-5 inhibitors, prostaglandin analogs, or endothelin antagonists should be used for the treatment of sarcoidosis-associated pulmonary hypertension.