Ongoing theft from library patrons may be the work of a determined thief, one who will not be deterred by the crimeproofing techniques that often stop less committed criminals. This type of theft can be deterred when the library staff makes their patrons aware that successful deterrence depends on them not abandoning their valuables. Other staff interventions, such as cautionary signage and an increased staff presence in troublesome areas, contribute to success but will be relatively ineffective unless patrons maintain control of personal valuables.