Description: Background: Shift work has been hypothesized as a risk factor for obesity. In this study, we investigated the association between current shift work and body mass index (BMI) among female nurses in Korea. The relationship between duration of shift work and BMI of the participants was also evaluated. Methods: This cross-sectional survey evaluated participants in the Korean Nurses' Survey, conducted from October to December 2011, using web-based self-administered questionnaires. A total of 9,989 nurses were included among 10,000 who registered on the survey web site (5,287 shift workers and 4,702 non-shift workers). Current shift workers were divided into tertiles of shift work duration (0.08-3.00 years, n = 1,732; 3.08-6.75 years, n = 1,731; and 6.83-38.00 years, n = 1,686). The BMI thresholds of overweight and obesity were 〉=23 kg/m2 and 〉=25 kg/m2, respectively. Data were analyzed using SPSS software. Results: Mean participant age was 33.2 +/- 8.6 years and the mean BMI was 20.9 +/- 2.5 kg/m2. There were statistically significant differences in current smoking status, regular drinking habit, dietary habits, regular exercise, sleep problems and self-perceived health status according to duration of shift work. The overall prevalence of overweight/obesity (18.6%) and obesity (7.4%) increased significantly as shift work duration increased from the lowest to highest tertile (P for trend