This paper studies the socio-economic determinants of violence in the seven most important cities in Colombia. Derived from theories rooted in classic works, including Becker's paradigm, criminal inertia, social disorganisation, urbanism and strain, we formulate several hypotheses on the socio-economic determinants of violence. To test these hypotheses, a dynamic panel data analysis is employed. The analysis shows that cities’ deprivation and high population density are strong predictors of homicide rates. Comparing the results among Colombian cities, we find support indicating that city-level homicide rates are influenced by the city's level of development. Moreover, we find evidence that economic growth, inequality, poverty and human capital influence violence in the cities studied, which could generate negative effects on the economic and social development of Colombia.