The diverse functions of the brain are mediated by neurons and glia whose phenotype is defined by a dynamically maintained set of gene transcripts, or 'transcriptome'. Large-scale analysis of gene expression in postmortem brain using microarray technology has the potential to elucidate molecular changes that occur in disease states. There are unique challenges associated with studies of postmortem brain, including limited sample sizes and variable clinical phenotypes that are typical of complex disorders. Nevertheless, recent microarray-based studies have implicated both individual dysregulated genes and abnormal patterns of gene expression in brain disorders.