Three factors that might help explain the extent to which physicians counsel patients to quit smoking and lose weight were examined: counselling self-efficacy, training in behaviour change and beliefs about causes of smoking and being overweight. More aggressive counselling was defined as counselling more patients per month and following up on counselling recommendations. Questionnaires were returned by 85 health maintenance organization physicians. As predicted, physicians with a stronger sense of counselling self-efficacy, and those who had received education in health behaviour change techniques were more aggressive counsellors. Motivational strategies were also explored. Physicians' beliefs about the causes of smoking and being overweight were related to the use of some types of strategies. Implications for increasing physician counselling patients to make behaviour changes are discussed.