ON November 20, 1995, more than one hundred substance-abuse experts gathered in Chantilly, Virginia for a meeting organized by the government’s top research agency on drug abuse. One topic for discussion was whether the agency, the National Institute on Drug Abuse (NIDA), which is part of the National Institutes of Health, should declare drug addiction a disease of the brain. Overwhelmingly, the assembled academics, public-health workers, and state officials declared that it should.