The study collected data prior to and after the implementation of the new determinate sentencing law. A probability sample of district court files was drawn from all felony filings from January 1, 1979, through August 30, 1980. The data collected pertained to offender and offense characteristics as well as case disposition. Initial analysis examined the distribution and frequencies of the data elements. Then, several variables were collapsed and recorded from information provided by the frequency output. Several variables were created: offenses committed before and after the effective date of the presumptive sentencing law, a plea bargaining indicator, most serious offense at filing, and most serious offense at conviction. The statistical analysis techniques used included frequencies, bivariate and multivariate analysis, analysis of variance and covariance, and discriminant analysis. No significant differences were found between the pre- and post-groups with respect to social characteristics, criminal histories, and the characteristics of crimes charged. Contrary to some of the previous research on determinate sentencing, this study found that determinate sentencing had little or no impact on sentencing practices in Colorado. Specifically, there was no increased reliance on plea bargaining or increase in average prison time served. This means that the anticipated reduction in sentencing disparity has not occurred. The Colorado determinate sentencing law decreased judicial discretion in sentencing, but it may have enhanced the discretionary power of prosecutors to produce no net change in sentencing outcomes. Tabular data and 14 references are provided.