Security problems characteristic of each type of library are identified. 'Inside' security procedures described for school libraries include (1) increasing accessibility of resources (reduces the need for theft), (2) building rapport with library users, (3) experimenting with methods to combat the nonreturn of media center materials, and (4) providing door checks. Other 'inside' security measures described for school libraries are improving the interior design to facilitate supervision and safety as well as installing electronic security systems. Among the 'outside' security procedures for school libraries are random police visits to the school. 'Inside' security measures for university libraries include exit guards and turnstiles. 'Outside' measures include campus police surveillance and presence in the library as well as private police hired specifically for library security. 'Inside' security measures for public libraries encompass the use of 'collectors' to visit the homes of delinquent borrowers and the installation of electronic security systems to detect theft attempts. 'Outside' measures may include a scheduled police presence and surveillance or assistance on demand. The article provides the outline of an inservice security training program.