The Quay classification system for the purpose of inmate management uses a factor-analysis technique to identify five personality factors: (1) inadequate-immature, (2) neurotic-conflicted, (3) unsocialized aggressive or psychopathic, (4) socialized or subcultural delinquents, and (5) subcultural-immature delinquents. At the correctional institution studied the five factors are collapsed into three: (1) inadequate-immature, (2) aggressive, and (3) normal. After an inmate has been classified at admission, he is placed in a living unit with other inmates similarly labeled. In addition to the Quay classification units, which are designed for the purpose of inmate control and order, there are program units for treatment. Unlike the Quay units, which house inmates of similar personality types, the program units are composed of inmates from all three of the Quay units. Inmate behavior under this system was determined through participant observation, interviews with staff and inmates, and analysis of the disposition of incident reports. Behavior displayed in the Quay units was congruent with the behavioral label of each unit; however, the Quay unit behavior of inmates changed when they participated in program units. While labeling theory appears to explain some of the behavioral manifestations, structural components (the functioning of the institution) also explain some of the behavior. The structure of the institution concentrates inmates by behavior type so that labeled behavior is reinforced through inmate interaction in the Quay units. While the establishment of program units provides relief from the Quay unit behavioral stimuli, when returned to the Quay unit, the labeled behavior of that unit resumes. Such inmate behavior must be considered when examining the impacts of various classification systems. Notes, a list of 11 references, and graphic data are provided.