Inflammatory processes in the brain have been implicated in both acute and chronic neurodegenerative disease. One of the most studied inflammatory mediators in this respect is the cytokine interleukin-1 (IL-1), which has diverse actions in the central nervous system and mediates a wide variety of effects, including the host defense responses to local and systemic disease and injury. Both pre-clinical and clinical data suggest a role for IL-1 as a key mediator of cell death in acute neurodegenerative conditions, such as stroke and head injury. IL-1 has also been implicated in a number of chronic diseases, including Parkinson's and Alzheimer's disease, as well as in epilepsy. Constitutive expression of IL-1 is very low in normal brain, but is up-regulated rapidly in response to local or peripheral insults. The mechanisms regulating the expression IL-1 are not well defined, but appear to involve multiple effects on neuronal, glial and endothelial cell function. Therefore, the IL-1 system represents an attractive and intensely competitive therapeutic target.