In this issue, Alberto Concha-Eastman directs our attention to the crucial question of violence as a public health issue. Dr Concha-Eastman, a Colombian, has first hand experience of taking charge of a violence prevention programme in his home city of Cali, where homicide rates are among the highest in the world. The inadequacy of a traditional policing model for understanding the upstream determinants of violence and developing rational joined up policies to prevent it is made clear in the framework put forward. This framework proposes three tiers of understanding: at the top there …