Results suggest that gun behaviors among juveniles are largely driven by gang membership, while ready access to guns, fear of the street, and the risks of arrest influence adult behaviors. The findings support the conclusion that juvenile or younger offenders are more willing than older offenders to carry and use firearms, suggesting a more fluid gun market for younger offenders. Nearly two-thirds of each age group reported ready access to firearms and that over half of the adult and juvenile arrestees disclosed owning or possessing a gun at some point in their life. Of the subsample of arrestees who reported previous experience with guns, juveniles were four times as likely to report carrying a gun on a daily basis and twice as likely to indicate that they had fired a gun in the last year when compared to adults. In reference to deterrence, more than half of respondents indicated that they were more afraid of the penalties associated with gun possession than confronting an armed person on the street; however, less than half of juveniles and adults reported that they considered the penalties of gun use before carrying out gun behaviors. These findings suggest that for juveniles the deterrence message may be more efficacious for youth who are only marginally involved in the violent subculture. Once juveniles have become involved with guns (and often gangs) the deterrent effect of arrest or threat of punishment diminishes; the youth most heavily involved in gun use may be the least likely to be influenced by deterrence messages. Data were drawn from a larger research project examining firearm involvement in St. Louis. Tables, reference, appendixes A-B