INTRODUCTION AND OBJECTIVES:Our aim was to investigate prospectively the association between two major cardiovascular risk factors: smoking and weight gain. METHODS:We prospectively evaluated 7565 individuals taking part in a dynamic cohort study over a median follow-up period of 50 months. Self-reported weight and physical activity levels had been validated previously. The adjusted mean difference in weight gain relative to never-smokers (the reference group) was estimated for different levels of tobacco exposure. RESULTS:After adjusting for age, baseline body mass index, sedentary lifestyle, changes in physical activity level, total energy intake, fiber intake, food consumption between meals, and sugary soft drink, fast food and alcohol consumption, it was found that individuals who stopped smoking during follow-up had a greater relative weight gain: men 1.63 kg (95% confidence interval [CI], 1.07-2.19 kg), and women 1.51 kg (95% CI, 1.11-1.91 kg). In addition, active smokers had a greater weight gain than never-smokers: men 0.49 kg (95% CI, 0.11-0.87 kg), and women 0.36 kg (95% CI, 0.07-0.65 kg). CONCLUSIONS:Individuals who stopped smoking during follow-up and active smokers both experienced significantly greater weight gains than never-smokers. This association between cardiovascular risk factors should be taken into account when developing prevention programs.