This Account reviews our laboratory's research in biomaterials. In one area, drug delivery, we discuss the development of materials that are capable of releasing macromolecules such as proteins and peptides, intelligent delivery systems based on magnetism or microchip technology, new degradable materials such as polyanhydrides, and noninvasive approaches for delivering molecules through the skin and lungs. A second area, tissue engineering, is also discussed. New polymer systems for creating cartilage, blood vessels, nerves, and other tissues are examined.