Five hypotheses are derived from theories about the inmate social organization of prisons. Interview and record data are gathered in a hospital serving imprisoned narcotic addicts. A Guttman scale is constructed, and associations are measured. The results generally affirm that a prison code is an institutional product expressive of the norms of a prisoner social organization, which serves to help inmates overcome the deprivations of prison living. Evidence also indicates that individual ties to the outside community, as well as individual expectations of possible legitimate rehabilitation, affect the solidarity of that prison social group.