Inmates were interviewed and tested in nine Federal prisons. Research questions sought to determine if learning disabled persons can be identified by behavioral characteristics in lieu of standardized testing instruments; if such persons have lower syntactical language development and lower cognitive processing skills than average adults; if a relationship can be demonstrated betweeen their language and their cognitive functioning; and if these inabilities are independent of factors such as sex, intelligence quotient, years in school, race, and psychopathology. Findings showed that all the inmates selected were lower in language and cognition as compared with normal subjects in and out of prison. The most important outcome of this study is the establishment of valid techniques for the identification and diagnosis of learning problems among inmates, which may be used with juveniles in order that remedial efforts can be initiated as soon as possible. Demonstration projects should be initiated to deliver development programs to learning disabled inmates as well as to learning disabled juveniles at risk, whose language and cognitive skills could thereby be improved to promote effective adult functioning before they become labeled in the criminal justice system. Tabular data and over 300 references are given.