On the cover: Schematic of the balance between NO and reactive oxygen species (ROS) that modulates NO bioavailability. When ROS production is increased, tetrahydrobiopterin (BH4) generation is reduced, and endothelial NO synthase (eNOS) produces superoxide (·O₂^–). Excess generation of ·O₂^– by different sources (NADPH oxidase, uncoupled eNOS, xanthine oxidase, myeloperoxidase, cyclooxygenase, mitochondria) will reduce NO bioavailability and convert NO into peroxynitrite (ONOO^–), which has deleterious effects. Reduced activity of superoxide dismutase (SOD) will also result in enhanced ROS accumulation in the vascular wall. COX indicates cyclooxygenase; FAD, flavin adenine dinucleotide; MLP,myeloperoxidase; NADPH, reduced nicotinamide adenine dinucleotide; XO, xanthine oxidase. (See page 32.)