Findings show that offenders who sexually penetrated children and teens in the offenses for which they were convicted had lower reoffending rates than offenders whose conviction offense involved adult victims. Those whose conviction offense was rape had the highest rates of rearrest for the same offense within 5 years compared with offenders whose victims were children or teens. Still, the overwhelming majority of all arrestees in the register's listed sex offender types did not recommit the sex crime for which they were first arrested in 1990. These findings fail to provide support for assumptions underlying sex offender registration and community notification laws, i.e., that all types of sex offenders compulsively repeat their crimes at a similarly high rate of reoffending. The study used Illinois arrest data for 1990 to 1997 compiled by the Illinois State Police. The Illinois criminal history database included approximately 17,000 sex-offense arrestees who were involved in approximately 26,000 arrests that culminated in 34,668 sex offense charges from 1990 to 1997. Charges were classified as specific types of sex crimes based on type of sexual behavior and victims' ages. Rearrest was used as the measure of reoffending. Reoffending was determined for any crime, the same crime, and any sex crime after 1, 3, and 5 years. 5 figures and 29 references