During the 1990s, in response to public dissatisfaction over what were perceived as ineffective crime reduction policies, 25 states and Congress passed three strikes laws, designed to deter criminal offenders by mandating significant sentence enhancements for those with prior convictions. Few large-scale evaluations of the impact of these laws on crime rates, however, have been conducted. Our study used a multiple time series design and UCR data from 188 cities with populations of 100,000 or more for the two decades from 1980 to 2000. We found, first, that three strikes laws are positively associated with homicide rates in cities in three strikes states and, second, that cities in three strikes states witnessed no significant reduction in crime rates. © 2004 Academy of Criminal Justice Sciences.