Broad reforms which have been adopted in 20 States fall into three categories: determinate sentencing, presumptive sentencing, and sentencing guidelines. During the last two decades, nearly all States have enacted laws establishing prison terms for crimes committed with deadly weapons. Most of these laws require mandatory minimum sentences, typically 1 or 2 years for first offenders. Most laws also provide for enhancing the sentence beyond that which would normally be given for the felony. Research into the impact of new sentencing laws on prisons and crime rates found little relation between sentencing laws and prison and crime variables. Some sentencing reforms, however, did exhibit relationships; presumptive sentencing led to more prison admissions and a higher prison population, and sentencing guidelines were followed by a lower prison population. These impacts differed greatly from State to State, and their magnitudes were usually small. On the other hand, determinate sentencing was followed by a sizable increase in the prison term index, resulting in longer sentences. Regression analysis found statistically significant increases in murder and robbery rates after sentencing guidelines and in robbery rates after presumptive sentencing laws went into effect. Weapon laws were followed by statistically significant, but small reductions in murder and robbery. Similar patters were found with respect to the impact of speedy trial laws. It is concluded that sentencing laws are not responsible for the growing prison population and that they do little to dampen crime rates. 513 references and 17 tables