Nitric oxide, recently named"Molecule of the Year"by the journal Science, impinges on a wide range of fields in biological research, particularly in the areas of biomedicine and cell and organismal biology, as well as in fundamental chemistry. This volume and its companion Volume 268 highlight methods used to research the physiology and toxicity of nitric oxide in cellular and organismal systems. It will be a valuable resource for the experienced researcher as well as for those newly entering the field.