"And I've done them, too," chuckled Allen Price, a 43-year-old methamphetamine addict from Oakland, Calif.
So when a friend told him about a 12-week program in San Francisco that would pay him up to $40 per week just to stay clean, he decided it was just what he needed.
For five weeks since, he has trekked to a clinic several times a week to submit a urine sample, and pick up a few dollars for testing negative.
"What appealed to me was the positiveness of it," he said. "It is a motivation. Stay off drugs and get some benefits out of it. Why not give it a try?"
The idea of paying people to stay clean has caught on around the country amid a growing body of research indicating the practice can help keep addicts off drugs.
Smokers in a two-year study at the University of Florida can get vouchers redeemable at Target, Wal-Mart or Amazon.com if they pass a test on whether they have had a cigarette.
A study of 415 cocaine and methamphetamine users published last October in the Archives of General Psychiatry found that they stayed in treatment longer if they had a chance to win a prize.
Dr. Lisa A. Marsch, a researcher with the National Development and Research Institutes, runs a program at St. Luke's-Roosevelt Hospital Center in New York that offers teenagers medication, counseling and reward vouchers for testing clean for drugs like heroin.
"It can be a very powerful technique," she said. "If it increases their motivation to stay clean even a little, it's worth doing."
Teens in Marsch's program must submit three urine samples a week. Pass, and the patient gets a voucher that can be used to buy something. The amounts start small but rise with every clean result. The second test might be worth $3.75, the third, $5. A person who remains drug-free for two months could earn as much as $596 in all.