More than 100 years have passed since the first description of sarcoidosis by Hutchinson1 and the identification of sarcoid granulomas by Besnier,2 Boeck,3 and Schaumann,4 but the causative agent or agents of sarcoidosis still have not been identified. However, in these intervening years, considerable knowledge has accumulated about the pathogenesis and the molecular events that lead to the granulomatous reaction. Clinical evaluation has shed some light on this systemic disease; pathology and immunology have contributed to our understanding of the inflammatory process. More recently, genetics and molecular biology have opened new avenues of research for this still enigmatic disease. There is some hope that new techniques provided by molecular biology, employing samples from bronchoalveolar lavage and biopsies, might elucidate the causative agents behind this disease and define the genetic modifications that make some people prone to developing sarcoidosis.