There is a growing concern about the extent of gun possession and use among criminals in the United Kingdom. However, variations in the estimates of gun involvement among offenders are argued in the National Criminal Intelligence Service (NCIS) report to be the result of the current lack of consistent data on firearms. This article attempts to help fill the gap in research knowledge about illegal gun possession among active offenders by drawing on the offender’s perspective. It provides new information on gun ownership and use among arrestees currently held in police custody suites. Data on illegal guns were collected as part of the New English and Welsh Arrestee Drug Abuse Monitoring program. The study consisted of a 3-year, rolling program of surveys, interviewing arrestees and covering 16 locations in England and Wales from 1999 to 2002. The survey showed that about one-quarter of arrestees interviewed said that they had owned or got hold of a gun at some point in their lives and about one-tenth had done so in the previous 12 months. The most common illegal gun possessed was a handgun and the most common reason for possessing a gun was for protection. There are a number of intervention strategies that can be used to target gun possession and use of guns in criminal activity, however in order to implement these strategies and programs effectively, it is important to develop a broad knowledge base of the extent, nature, and purpose of gun possession among offenders. Tables and references