During the last 40 years penological researchers have attempted to analyze behavioral patterns of prisoners in order to promote better security, control, rehabilitation, and crime prevention. While some researchers take the position that the informal social system develops as a functional response to the pains of imprisonment, others argue that the informal social system is imported into the prison from a nonprison thief subculture. Through a comprehensive search of the literature, this paper provides a current analysis of both models of the inmate social system. Current values, codes, mores, and behavioral patterns of inmates are investigated in an attempt to bridge the gap between the two theories on prison behavior. As part of the study, questionnaires were distributed to 250 present and former prison inmates of a maximum security facility. A total of 212 questionnaires were completed. These questionnaires provided data on demographic, socioeconomic, and social characteristics of the respondents before and during imprisonment. The collected data partially supported the study hypotheses. It is concluded that the informal social system which exists in prisons is factionalized into various subcultures resulting from ties and affiliations imported into the prison from the urban lower class. A literature review, an extensive bibliography, an appendix, tables, and footnotes are included. (Author abstract modified).