Sentencing guidelines address both the decision about whether or not to incarcerate and, if imprisoned, the sentence length. The statute establishing the Pennsylvania Commission on Sentencing specifies that guideline sentences should at least consider the severity of the crime, the defendant's prior record, and whether a deadly weapon was used in the crime. The general approach to guideline development is to establish a sentencing chart or matrix. One dimension of the matrix is normally an offense score which includes the severity rank of the crime and may include enhancements such as bodily injury to the victim or use of a firearm in the commission of the crime. The second major category of factors relate to the offender's background (offender score). Descriptive sentencing guidelines focus on describing past sentencing practices. Recent criticism of the descriptive mode of guideline development has argued that descriptive guidelines' reliance on past sentencing practice is not justifiable on theoretical grounds. This has led to the development of prescriptive or policy-based guidelines based in the intent to issue sentences that reflect a uniform policy. The prescriptive approach diminishes the likelihood that urban dominated practices will be adopted as the sentencing standard. It also has greater potential for expressing a policy that will revise past sentencing disparity. Graphic illustrations and 26 footnotes are provided.