The study is in response to an Request for Applications entitled Ancillary Studies in Heart, Lung, and Blood Disease Trials which was released by the NHLBI in June 2000 to conduct mechanistic studies in clinical trials related to heart, lung and blood diseases. Specifically, this initiative focuses on the utilization of patients and patient materials from such trials to study the mechanisms underlying the interventions, the mechanisms of disease pathogenesis, surrogate markers or biomarkers of disease activity and therapeutic effect and the mechanisms of human cardiopulmonary and hematologic function. Studies aimed at accelerating the development of new technologies within the context of the mechanistic investigations are also encouraged.