Primary care physicians are in a unique position to detect patients with substance use related problems and initiate treatment at an early stage when it may be more successful. To evaluate current knowledge, attitudes, and practices of primary care physicians in the United States regarding the detection of substance use related problems, a national telephone survey of practicing primary care physicians was conducted in 1999. A total of 648 randomly selected family and general practitioners, internists, pediatricians, and OB-GYNs were interviewed regarding their perceived preparation to diagnose selected health conditions, their perceived difficulty discussing selected health conditions with patients, and their perceptions of the effectiveness of available treatments for selected health conditions. Findings suggest that primary care physicians in the United States perceive themselves as being less prepared to diagnose substance "abuse" than other chronic conditions. They additionally find it more difficult to discuss this topic with their patients, and are more skeptical about the effectiveness of available treatments. Because the social, economic, and health consequences of untreated substance misuse negatively affect the quality of life for so many patients and their families, developing new approaches to improving the attitudes and screening behaviors of primary care providers vis-à-vis substance use disorders should continue to be an important priority.