ALG-2is a recently described pro-apoptosis gene that codes for a Ca2+-binding protein involved in T-cell receptor-, Fas- and glucocorticoid-induced cell death. We have usedin situhybridization histochemistry to examine the regional distribution of ALG-2 mRNA in the brain of 3- and 24-month old rats. There was widespread, predominantly neuronal distribution ofALG-2 mRNA throughout the brain. Areas expressing high levels included the granule and pyramidal cell layers of the hippocampus, choroid plexus, area postrema, and a number of hindbrain nuclei.ALG-2 mRNA levels in aged rats were not significantly different to young animals. The pattern of expression ofALG-2 mRNA in adult brain is similar to other apoptosis-related genes and suggests it may be involved in neuronal survival.