BACKGROUND AND OBJECTIVES: More than two thirds of Americans are overweight or obese. Physician counseling may help patients lose weight; however, physicians perceive these discussions as somewhat futile and time-consuming. An effective and efficient tool for smoking cessation is the Five A's (Ask, Advise, Assess, Assist, and Arrange). We studied the effectiveness of the Five A's in weight-loss counseling. METHODS: We audiorecorded primary care encounters between 40 physicians and 461 of their overweight or obese patients. All were told the study was about preventive health, not weight specifically. Encounters were coded for physician use of the Five A's. Patients' motivation and confidence were assessed before and immediately after the encounter. Three months later, we assessed patient change in dietary fat intake, exercise, and weight. RESULTS: Generalized linear models were fit adjusting for patient clustering within physician. Physicians used at least one of the Five A's often (83%). Physicians routinely Ask and Advise patients to lose weight; however, they rarely Assess, Assist, or Arrange. Assist and Arrange were related to diet improvement, whereas Advise was associated with increases in motivation and confidence to change dietary fat intake and confidence to lose weight. CONCLUSIONS: Similar to smoking cessation counseling, physicians routinely Asked and Advised patients to lose weight; however, they rarely Assessed, Assisted, or Arranged. Given the potential impact of using all of these counseling tools on changing patient behavior, physicians should be encouraged to increase their use of the Five A's when counseling patients to lose weight