In a pilot health promotion program for couples, we aimed to build on re-evaluation of attitudes to health occurring early in marriage, and social support provided by partners, to address the weight gain and physical inactivity which may follow marriage. A randomized controlled trial lasting 16 weeks used six modules focusing on nutrition and physical activity but including information about alcohol and smoking. Thirty-four of 39 couples enrolled completed the study. Self-efficacy for diet and physical activity increased significantly in the program group while ranking of barriers to healthy behaviours decreased and ranking of beliefs about the benefits of health behaviours increased relative to controls. Intake of fat, take-away foods and alcohol decreased, and consumption of fruit, vegetables and reduced-fat foods increased significantly in the program group. Physical activity in the program group increased by the equivalent of 50 min of brisk walking weekly but did not differ significantly from controls. Cholesterol fell significantly by 6% more in the program group than controls. In focus groups, participants unanimously found the program valuable. Health promotion programs designed for couples can achieve short-term changes in behaviour and risk factors. Larger trials with longer-term monitoring, incorporating feedback from focus groups and cost-benefit analysis, are in progress.