The research was based on interviews with inmates and on observations. The findings indicate that the type of inmate social structure and the way it operates is a function of access to consumer goods and how these are obtained. This is closely related to whether the prison is a closed or semiopen institution, although as the study of the prison for recidivists showed, the internal organization of work also makes a difference. If the materials used in a factory located on the prison grounds (closed prison) have no market attractiveness and the tools are not too useful for illegal production, then goods will be obtained through the exploitation of fellow prisoners; therefore, the informal inmate social structure basically is designed for the obtaining of consumer goods. The skills and qualification of inmates, particularly their ability to use tools for economic advantage, are also important factors, but in the main, the character of the structure depends on access to goods and the strategy for obtaining them. These two variables are apparently determined by the type of institution and the type of production. If changes are made in the penal institution which considerably affect the access of consumer goods and the strategy for obtaining them, then the inmates will tend to change behavior to produce maximum profits within the new structure. One note and 23 references are provided.