ntravenous-drug users who spread disease by sharing dirty needles and engaging in unprotected sex are responsible for more than a third of all the AIDS cases in the United States and more than half of the new cases of hepatitis C. Addicts will continue to drive these epidemics until the country takes a more enlightened approach to drug treatment. That means discarding the laws that criminalize needle possession because such laws encourage addicts to share needles. It also means developing large-scale treatment programs that admit addicts right away instead making them wait months or years. A blueprint for such a program has been put forward in California, which has embarked on the most ambitious drug treatment effort yet seen in the country.

Many states still make it a misdemeanor to possess needles, and a few states actually direct sanctions at pharmacists who sell needles without a prescription. In contrast, Gov. Arnold Schwarzenegger of California courageously signed an important needle-access bill this week, similar to one that was vetoed twice by his predecessor, Gray Davis. The new law will allow pharmacists to sell as many as 10 syringes without a prescription to any adult in participating cities and counties. The law expires in 2010, when state authorities will evaluate its usefulness.

The state also needs to revisit an absurdly restrictive law that requires localities to declare states of emergency - over and over again, every two or three weeks - to run vital programs that let addicts exchange dirty needles for clean ones. These programs slow the spread of AIDS infections - without spreading addiction - and serve as a gateway to treatment.

Addicts seeking treatment in California are having an easier time getting it thanks to Proposition 36, which offers drug treatment to nonviolent drug offenders. In the last two years, more than 65,000 people have entered treatment; many of them would have otherwise gone to jail . A study describing how effective the program has been is due by year's end. But a report released just this week by a research group at U.C.L.A. provides reasons for cautious optimism. For example, roughly one in three people who entered the program completed it - which is par for the course. And about half the people being treated were participating in a treatment program for the first time, even though many had been addicted for a decade or even longer.

Outpatient programs are available, but there appears to be a shortage of residential programs, which are crucial for Methamphetamine addicts. They make up the largest bloc of addicts and often need months to recover. Residential programs also help addicts of all kinds who live on the streets or in drug-saturated households where outpatient rehabilitation would be difficult. Criminal justice officials need to shed their biases against Methadone maintenance for this program to succeed with Heroin addicts, who are the most difficult to treat.

California is already learning that there are many more nonviolent drug addicts in need of treatment, clogging the jails and courts, than many of us thought. If the new regime rehabilitates even a third of those people, prison costs and blood-borne infections like AIDS should decline noticeably.