Because the law came into effect during a period of declining crime rates, it has been widely assumed that the law has been responsible for a major share of California's crime decline, but no rigorous evaluation of the impact of the law has been reported. Accordingly, the current study analyzed arrests before and after the law went into effect in three cities--Los Angeles, San Diego, and San Francisco. The study was designed to determine how much crime in California was caused by specially targeted groups, how much difference the new law made in criminal sentences, and whether the new law was responsible for a significant decline in crime. Large samples of felony arrests were gathered in the three cities, and criminal records of felony offenders were analyzed. Results showed 1 in 10 felony arrests involved a defendant with either 1 or 2 prior strike convictions. More surprising, those who were eligible for the law's increased penalties did not decline as a percentage of those arrested in the first 2 years after the law. Because 90 percent of California criminals were not covered by three strikes, the potential impact of the law on crime rates was modest. The authors conclude that, because the arrest rate among persons not subject to three strikes penalties dropped as much as the arrest rate for the targets of three strikes, the law does not appear to be an important part of the general decline in California crime. References, tables, and figures