A national representative survey of primary care physicians (N=648) was conducted to determine how they deal with patients who have substance abuse problems. The survey revealed how physicians identify substance abuse in their patients, what efforts they make to help these patients, and what barriers they find to effective diagnosis and treatment. The most troubling finding of the survey was that 94 percent of the physicians failed to include substance abuse among the five diagnoses they offered when presented with early symptoms of alcohol abuse in an adult patient. Also surveyed were 510 adults currently receiving treatment for substance abuse. Most patients said their physicians did nothing about their substance abuse. These findings add up to an enormous lost opportunity. Substance abuse and addiction are the leading cause of death, disability, and disease in the United States. Primary care physicians have a unique opportunity to intervene to avoid these consequences. To avoid the missed opportunity, this report recommends that medical schools increase training in substance abuse, that primary care physicians screen patients for substance abuse, and that insurers provide for physicians talking to patients about substance abuse. (Contains 3 appendixes, 27 figures, and 30 references.) (JDM)