This dissertation is an evaluation of an intervention implemented to improve the adjustment of prisoners. The intervention, known as Decisions, is a structured educational model. It rests upon the assumption that criminals are poor problem-solvers and view themselves as victims of forces over which they have little or no control. Decisions attempts to cause enhanced prisoner adjustment by first causing improvement in problem-solving ability and a shift toward the internal dimension of personal control of prisoners. The literature review revealed three studies directly related to the underlying assumptions of Decisions. None of the studies lend any support to those assumptions. However, the literature does indicate that problem-solving ability and locus of control are related to prisoner adjustment. The literature reviewed also shows that the locus of control of prisoners is subject to at least short-term change via an intervention like Decisions. It was hypothesized that the experimental group would score significantly better on problem-solving scores and significantly more internal on locus of control scores at posttest and follow up. It was also hypothesized that the experimental group would score significantly better in adjustment at follow up. The analysis revealed a significant initial group difference on pretest locus of control scores, and on the scores of one adjustment scale. Attrition resulted in additional group differences on age and education. All analyses showed nonsignificant results. There were no significant differences between groups on posttest and follow up locus of control and problem-solving scores, nor on follow up prison adjustment scores. Only the variable age accounted for any significant variance of prison adjustment. Several interpretations of the results are offered. The first is that outcome is the cause of significant group differences both present at pretest and resulting from a high mortality rate. The second is that skewed distributions of two measures made it difficult for any change in the desired direction to be detected. A third and more plausible interpretation is that the intervention rests upon a weak theory. That is, neither the literature nor the data generated in this study support the assumption that prisoners are poor problem-solvers and externals. (Abstract shortened with permission of author.)