Federal mandatory sentences have raised the overall severity of punishment in drug and weapon cases, and they have probably made defendants more willing to assist in the investigation and prosecution of other cases. Further, because Federal mandatory sentences preserve substantial discretionary features, trial rates have not soared and process costs of true mandatory sentences have largely been avoided. These gains aside, Federal mandatory sentences produce many adverse consequences. Severity gains are substantially undercut by uncertainty effects, since mandatory sentences appear to be evaded in 30 to 50 percent of cases in which they apply. Given the high cost of mandatory sentences as they currently operate in the Federal system, it may be advisable to determine if their benefits (deterrence, uniformity, and cooperation) can be achieved by other alternatives. One such alternative is the sentencing guideline system authorized by Congress in 1984. The author contends that sentencing guidelines create a much greater degree of uniformity than the previous regime of unstructured judicial sentencing discretion. In addition, by fixing appropriate guideline sentencing ranges, guidelines can guard against what may be perceived as undue judicial leniency and can avoid excessive uniformity by basing the guideline calculation on appropriate, structured adjustments for the offender's role in the offense, his or her acceptance of responsibility, and mitigating personal circumstances. Sentencing guidelines can achieve a substantial degree of determinacy, predictability, uniformity, and even severity. The role of Congress in sentencing policy formation is discussed. 118 footnotes