This study examines the impact of white ethnic concentration on robbery and homicide in Chicago and New York City. As one of the first to disaggregate white ethnic populations, this study has the expectation that Italian-American concentration will have a stronger influence on robbery and homicide than any other white ethnic concentrations. This study is founded on prior qualitative research suggesting that the reputation of Italian-Americans influences the behavior of outsiders in their communities. The data show there is a significant and negative relationship between Italian-American concentration and the violent crimes robbery and homicide. This relationship only exists for white ethnic concentration with robbery. These patterns occur across both cities at three different aggregate levels. The results indicate that there may be particular characteristics about Italian-American ethnic concentrations which have dampening effects on the frequency of homicide and robbery in their communities; it is speculated that a reputation for Mafia involvement is one of the protective factors.