After making minor changes to the bill, regarded as the biggest change to the state's criminal-justice system in many years, the Senate approved it yesterday, 48-2.

Under its key provisions, nonviolent drug offenders in prison could be resentenced to an addiction-treatment program, and nonviolent offenders who behaved well and completed certain programs could be paroled more quickly.

All senators from the Philadelphia area voted for the measure. The House, which has approved previous versions of the bill in recent months, is expected to give final approval next week.

Gov. Rendell has pressed for the changes, and a Corrections Department spokeswoman said officials there supported the bill.

The hope is that with rehabilitation, fewer convicts would return to crime after their release, and that the state could slow the growth of a prison population that has quadrupled in the last quarter-century to 46,800.

Mandatory-sentence laws that were passed in the 1990s to punish violent criminals inadvertently sent nonviolent offenders away for long sentences, too, said Sen. Stewart Greenleaf (R., Montgomery).

"They were important bills, and they dealt with violent offenders, but it's having a broader effect than we anticipated, and it's important that we step forward and acknowledge that," said Greenleaf, a former county prosecutor who chairs the Judiciary Committee.

The bill also would divert to the state prison system hundreds of the approximately 30,000 convicts now serving their sentences in county jails, easing a financial burden on counties.