OBJECTIVE: To investigate the prevalence and the secular trends of obesity in a rural Swedish community with emphasis on the association with socioeconomic status and lifestyle. DESIGN: The Skaraborg Project cross-sectional population surveys were conducted in Vara, a rural community in the southwest of Sweden, every fifth year between 1977 and 2002. SUBJECTS: A total of 3365 residents (1634 men and 1731 women) aged 30-60 years. MEASUREMENTS: Obesity was defined as body mass index> or =30 kg m(-2). Information on ethnicity, marital status, socioeconomic status and lifestyle was collected by a questionnaire. RESULTS: In 1977-1982, the average prevalence of obesity was 14% in both men and women, and in 2002, the prevalence of obesity was 19% in men and 21% in women. The age-adjusted odds ratio (OR) of obesity in 2002 was 1.48 (1.00, 2.20) in men and 1.41 (0.97, 2.05) in women. Without the simultaneous increase in the level of education and leisure-time physical activity (LTPA), the risk of developing obesity could have been considerably higher; in men OR=3.08 (1.88, 5.03) and in women OR=2.72 (1.66, 4.44). In multivariate models, higher levels of education and LTPA were associated with protective effects on obesity in both men (OR=0.60 (0.43, 0.83) and OR=0.50 (0.45, 0.79)) and women (OR=0.73 (0.54, 0.98) and OR=0.57 (0.42, 0.78)), respectively. CONCLUSIONS: This study revealed an upward secular trend in the prevalence of obesity in a rural community in Sweden. Increasing levels of education and LTPA limit this ongoing development of obesity. Public health strategies for the prevention of obesity should consider the special condition in rural environments.