This article reviews the studies on 5-hydroxyindoleacetic acid in cerebrospinal fluid (CSF 5-HIAA) & serotonin (5-HT) in aggressive & suicidal behavior. The author also discusses the relationship between 5-HIAA, 5-HT, & depression, suicide intent & method, anxiety, & impulse control. He ends with 6 conclusions about this area of biochemical research, including the assertion that low 5-HIAA is often found in recent suicide attempters & depressed suicide attempters. (VM)