Sites for this study were the Denver District Court, the Philadelphia Court of Common Pleas, the Cook County Circuit Court in Chicago, and the Essex County Court in Newark, N.J. Primary data sources consisted of a reanalysis of data used in the Denver, Chicago, and Newark sentencing guidelines research, analysis of case records from Denver and Philadelphia, and interviews. Particular weaknesses in the methodology were a small sample and the use of a single set of variables to determine both the decision to incarcerate and the decision about length of incarceration when other analyses have shown that these decisions are influenced by different factors. The assessment of sentencing guidelines' impact on the exercise of judicial discretion found that compliance was lower than expected, sentence disparity was not reduced, and plea bargaining was unaffected. To the contrary, the failure of the guidelines model to accommodate plea bargaining practices appeared to be partly responsible for its ineffectiveness. The study concluded that two conditions must be met for guidelines to achieve their objectives: they must be given the force of law and they must include method of conviction as a determinative factor. Examples of sentencing guidelines are appended. The report includes tables and footnotes. For related material, see NCJ-84755. (Author summary modified)