To learn about cancer prevention services in primary care practices and to understand physician factors that affect the provision of these services. Survey of physicians and their patients in 1992. Cooperating physicians (n = 72) of a random selection of community general internist and family physician practices in New Hampshire and Vermont. Patients (n = 2775) of the study physicians for at least 1 year, aged 42 years or older, with no life-threatening threatening illness, who recently visited the physician. Proportion of sample patients per practice provided age- and sex-appropriate cancer prevention services in the previous year. In this primary care population, a high proportion of patients received appropriate services in 1992. A periodic health examination within the past year was an important predictor for the receipt of many cancer prevention services. Female physicians provided more periodic health examinations than male physicians; internists provided more than family physicians. The strongest determinant of receiving preventive services is having a periodic health examination. If clinicians and policymakers decrease emphasis on the periodic health examination as a major opportunity to provide indicated preventive services, they should ensure that a satisfactory alternative strategy is in place.