The DuPage County Domestic Violence Protocol includes a pro- arrest policy for the police. In keeping with the Illinois Domestic Violence Act of 1986, the policy includes the option of the police officer signing a complaint when the victim refuses to do so. Once arrested, domestic-violence offenders are likely to have a court appearance. The protocol discourages the State attorney's office from dismissing charges, even on the victim's request. The protocol provides sentencing guidelines for offenders who plead guilty or are found guilty. The study findings are based on analyses of police reports from January 1, 1992, until March 31, 1992. Police made 1,025 domestic-violence incident reports to the Family Shelter Service during the 3-month period. Of these, 690 involved male-to-female violence in which the alleged perpetrator was either the victim's husband, cohabiting partner, or a former husband or boyfriend. The recidivism measure incorporated police contacts that resulted in arrest and those that did not. The analysis examined the effects of arrest and prosecution on subsequent police calls and arrests within an 18-month period, following the initial incident. Logistic regression analysis shows that arrest significantly deterred subsequent domestic-violence incidents. The deterrent effect of arrest did not deteriorate over the 18-month period and was most pronounced for those offenders who had a previous history of police involvement for domestic violence. 3 tables, 1 figure, and 23 references