The role of guns and other weapons in violent acts has often been a subject of debate. The present study is based on a sample of 21,314 valid interviews with 20 year old Swiss men, representing over 70 percent of this cohort. The results show a much higher frequency of violence among owners of handguns and other weapons, but not of rifles. Gun owners also have been injured more often, and they suffer more often from psychiatric symptoms. A considerable proportion of violent gun owners had previous police contacts and court appearances, suggesting that policies designed to confiscate guns would be feasible. In a multivariate model, which considered a great number of conventional criminological variables (such as delinquent friends) and indicators of psychopathology, ownership of handguns and other weapons (but not rifles) turned out to be a very important factor in explaining violence leading to bodily injury.