Recent work suggests that some persons who commit suicide have altered neurochemistry in their brains. It remains unclear which of the many reported abnormalities are most reliably present and whether they reflect a specific psychiatric disorder or a disposition to violent impulsivity. A number of technical and interpretive problems must be clarified, but a postmortem test indicating that a subject was at high risk for suicide may eventually emerge. This approach would not be useful for ruling out suicide, since altered neurochemistry is not likely to be involved in every case.