The aim of this study was to assess the prevalence of night eating (NE) and associated symptoms in a population-based sample of Swedish twins. A total of 21,741 individuals aged 20-47 years completed a questionnaire in 2005/2006. NE was defined as >/=25% of daily food intake after the evening meal and/or awakening at least once per week with eating episodes. The prevalence of NE was 4.6% in men and 3.4% in women. Among obese men and women, the prevalence was 8.4 and 7.5%, respectively. Men and women with NE had 3.4 and 3.6 times higher risk of binge eating compared to individuals without NE. The risk of sleep-related problems was 1.6-3.4 times higher in men and 2.5-3.3 times higher in women with NE compared to those without NE. This epidemiological study has estimated the prevalence of NE in a twin population. It revealed that NE is 2.5 and 2.8 times more common in obese men and women compared to normal weight men and women. Furthermore that NE is associated with binge eating and sleep-related problems.