Under current Federal law, many persons with prior convictions for misdemeanor offenses pass criminal records background checks and legally purchase handguns. This retrospective cohort study involved 5,923 authorized purchasers of handguns in California in 1977 who were younger than 50 years old; they were identified by random sample. The main outcome measures were incidence and relative risk of first charges for new criminal offenses after a handgun purchase. Of the 5,923 authorized purchasers, 3,128 had at least one conviction for a misdemeanor offense prior to a handgun purchase, and 2,795 had no prior criminal history. Follow-up to the end of the 15-year observation period or to death was available for 77.8 percent of the subjects and for a median 8.9 years for another 9.6 percent. Handgun purchasers with at least one prior misdemeanor conviction were more than seven times as likely as those with no prior criminal history to be charged with a new offense after a handgun purchase. Among men, those with two or more prior convictions for misdemeanor violence were at greatest risk for nonviolent, firearm-related offenses such as weapon carrying, violent offenses generally, and Violent Crime Index offenses; however, even handgun purchasers with only one prior misdemeanor conviction and no convictions for offenses involving firearms or violence were nearly five times as likely as those with no prior criminal history to be charged with new offenses involving firearms or violence. 5 tables and 32 references