Weapons are used in approximately one quarter of all violent incidents and the majority of homicides in the US, and the UK. Despite their overwhelming contribution to violent harm, theories of weapon related behaviors are scarce, and little is known of their correlates. This paper reviews available theories of weapon related behavior and identifies a number of motivations for weapon carrying, such as self defense, victim coercion, causing harm and self presentation. Correlates of weapon carrying and weapon use such as age, gender, socioeconomic status, exposure to weapons and history of aggression are explored and a number of limitations to current research approaches are identified. The review concludes with a discussion of future directions for research. © 2009 Elsevier Ltd. All rights reserved.