Data on five aggressive &/or violent human behaviors were examined by computer to determine whether a relationship exists between the lunar synodic cycle & human aggression. Homicides, suicides, fatal traffic accidents, aggravated assaults & psychiatric emergency room visits occurring in Dade County, Florida were all found to show lunar periodicities. The suicide curve showed correlations with both aggravated assaults & fatal traffic accidents, suggesting a self-destructive component for each of these behaviors. The existence of a biological rhythm of human aggression which resonates with the lunar synodic cycle is postulated. (18 refs)