This report, by the California Department of Justice, presents findings for 1998, 1999, and 2000 regarding California’s Penal Code Sections 12021 and 12021.1, which restrict owning or possessing firearms by certain groups of individuals. The study was conducted to determine whether Sections 12021 and 12021.1 were effective deterrents to owning or possessing a firearm. Sections 12021 and 12021.1 restricts convicted felons, anyone addicted to narcotics, individuals with certain misdemeanor violations, and some people on probation from owning or possessing a firearm. The California Department of Justice examined more than 22,000 criminal histories extracted from a data file housing records on arrest, court disposition, and conviction. The results of the study are presented in Tables 1–66, and are grouped by county as well as statewide. The major findings of the study include a marked decrease in every category of arrest, court disposition, and conviction for the targeted offenses during 1998 through 2001. The only exception to this decrease occurred in cases where there was a previous conviction for a violent or serious offense. Another key finding was that other law violations were present in 39 percent of the convictions involving Sections 12021 or 12021.1, compared with 78 percent of all other convictions. The study also uncovered the fact that the typical time between release from prison and subsequent arrest for owning or possessing a firearm was 2 years and 5 months. Overall, the results shine a positive light on the deterrent effect of Sections 12021 and 12021.1.