This study will compare blood from healthy volunteers and with wound fluid and tissue samples from patients with acute and chronic wounds enrolled in other NIH studies. Chronic wounds, such as venous leg ulcers, pressure sores, ischemic ulcers and diabetic foot ulcers, affect more than 4 million Americans each year and cost about $9 billion to treat. The nature of these wounds is not well understood and treatments are not always successful, for unknown reasons. Blood collected from healthy volunteers will be used to prepare a model for studying various processes involved in wound healing.