The reports make it clear that it is not feasible to deny that Europe has youth groups that can be called street gangs; such groups exist and their various patterns are describable. Eurogang Program members have identified 50 cities that have gangs in 16 countries. The data reported here suggest some important conclusions about the relationship between European street gangs and violent behavior. First, the level, severity, and lethality of youth violence are, generally speaking, lower in European countries than in the United States. Second, once this general level of violence is taken into account, gang membership appears to have the same harmful effect on behavior for European youth as it does for American youth. Third, following a review of qualitative reports on European gangs, it was found that the nature of violence was varied and differentially motivated. Fourth, similar to American studies, gang membership has an impact on violence over and above the impact of association with delinquent peers. In all cases there is a gang effect on violent behavior. Within the contexts of American gang violence and European non-gang youth violence, this article tries to provide as systematic a view as possible of the relationship between European street gangs and violent behavior. Reports were used that were produced under the support of the Eurogang Programs, based on quantitative as well as qualitative data. All reports dealt with youth groups that fitted well into the Eurogang consensus definition of a street gang and that were describable in terms of the Maxson-Klein street gang typology. Tables, references