OBJECTIVE: Our purpose was to investigate if low levels of cerebrospinal fluid (CSF)monoamine metabolites of 5-HIAA, HVA and HMPG predict relapse in violent crimes. METHOD: Relapse in crime and level of CSF monoamine metabolites (5-HIAA, HVA and HMPG) was studied in a group of 29 murderers. The follow-up was 16 years. RESULTS: Fourteen of the 29 murderers were convicted of crime; nine of them committed violent crimes; one was convicted of a new murder. The differences in mean CSF monoamine metabolites were lower in subjects who relapsed into any type of crime, but only the difference in mean CSF HVA was statistically significant. CONCLUSION: The risk to commit new murder is very small in males who earlier have been convicted of murder. Low levels of CSF HVA is associated with an increased risk for relapse in any type of crime.