Obesity is consistently reported to have a positive association with the development of habitual snoring. Whether lifestyle factors modify the association between body weight and the future risk of snoring has not been examined. In a prospective cohort study, we evaluated the association of lifestyle factors and body mass index (BMI) with the development of snoring. The study population (497 men and 670 women aged 40-69 years) were drawn from an ongoing population-based cohort. At baseline, all participants were free of cardiovascular disease and snoring at night. Information on lifestyle factors and snoring frequencies was obtained from interviewer-based questionnaires. During the 4-year follow-up, 533 participants reported new onset snoring. After adjusting for age, sex, and other potential risk factors, overweight persons with a BMI of ≥25 kg/m2 were found to have a 48% excess (95% confidence interval, 10% to 100%) in the odds of developing snoring compared with those with a BMI of <23 kg/m2. In particular, we found that alcohol drinking and frequent exercise modify the association between BMI and the development of snoring; alcohol drinkers showed a stronger association than abstainers and persons who did not frequently exercise showed a stronger association than those exercising 4 days per week. We observed that even overweight persons who drink alcohol or do not exercise frequently had a higher chance of becoming snorers. Further evaluations are warranted to confirm whether abstaining from alcohol and frequent exercise can help prevent future snoring.