There is an accumulating body of research suggesting that suicidal behavior may be associated with abnormalities of the central serotonin system. Other monoaminergic, peptidergic, and neuroendocrine systems have been implicated as well. A review of studies that examine neurobiological variables in postmortem tissue of suicide victims and controls reveals that investigators in most instances have viewed age as a confound to be controlled rather than considering it as a variable of interest. However, the close associations between aging and increased suicide rates, and the knowledge that the functional integrity of many of these same systems changes with normal and abnormal aging processes, raise the possibility that biological aging contributes to suicide risk, and that the underlying neurobiology of suicide in the elderly differs from that of younger people. The few available studies that did examine the association of age with neurobiological measures indicate directions for future research into the role that aging may play in determining the biological bases of suicide risk.