Many offenses are committed by two or more people working together. This article presents a review of some of the better known characteristics of co-offending, and discusses of the ways in which offenders vary in their preference for co-offending or solo-offending, and the ways in which offenses vary between offense types. Co-offending occurs more in young offenders than in older ones, and is often investigated by one of the co-offenders. Also, co-offending can be either a simple or a complex operation that usually takes place in small offending groups, often takes place within relatively homogenous offending groups, and typically occurs within changing constellations or partners. Following a brief discussion of the group influence, social selection, and instrumental perspectives, the author contends that both the social exchange theory and the exchange goods of co-offending theories may be used to develop a causal model to explain why co-offending shares the characteristics that it does. Co-offending is essentially a mechanism by which material and immaterial goods are exchanged. References