There are two general categories of missing persons: (1) the intentionally missing, which includes runaways, custody kidnappings, loan skips, and fraudulent life insurance claimants; and (2) the unintentionally missing, who may be subjects of medical recall, alumni, stockholders, and insurance policyholders. One category of reference material available to the investigator is public records, which are easily accessible. These include telephone directories, city directories, trade and association directories, and vital statistics such as certificates of births, deaths, marriages, divorces, and automobile registrations and drivers licenses. Confidential records compose a second category of written information. Included here are social security and internal revenue and military files. Although these records are more difficult to obtain, these references may be open to a spouse or relative of a missing person or to an agent of such persons (tracer). Tracers can also be aided in their searches by developing a network of communication and contacts with persons having access to relevant information. Interviewing under pretext (pretending to be making a survey) and the use of disguises are all tools of the trade. The tracer should also use his/her imagination in developing information sources relevant to a particular case; for example, if a missing person is known to be an auto racing fanatic and has subscribed to several racing magazines in the past, a contact might be developed in the subscription department of those magazines. The appendix describes how to locate various information sources. (Author summary modified)