A large burden of cancer morbidity and mortality is potentially preventable by changes in personal health behaviors. Health behavior advice (HBA) by primary care physicians, who provide basic health care to most Americans, holds great promise as a strategy to alter cancer-related health behaviors and to reduce morbidity and mortality. One potentially powerful strategy is the use of illness visits as a 'teachable moment'(TM) for health behavior change. Our in-depth analysis of audio recorded physician-patient interactions has led to new discoveries of the communication elements of a TM. First, effective TM's involve linking a health behavior to a salient patient problem and positioning the health behavior as a problem. Persuasion is accomplished by suggesting that changing the health behavior will improve the patient's salient concern. If done skillfully, the patient accepts the portrayal of the health behavior as a relevant problem and exhibits uptake of the health behavior change talk, possibly expressing a commitment to change. Our data reveal that TMs occur in 20% of health behavior discussions between physician and patient. More frequent (43%) , however, are TM 'attempts' which fail to engage the patient. These attempts lack two essential aspects of good patient-centered advice 1) eliciting the patient's readiness to change and 2) responding in alignment with the patient's expressed stage of change. We also observed 'missed opportunities' (20%) where the health behavior advice failed to link to a salient patient concern.