This study was undertaken to examine the prevalence of obesity and its determinants among adults in a rural area of Chile. A community-based cross-sectional study was conducted in April-June 2004 in San Carlos (8th region). Height, weight, and waist and hip circumferences were measured for 603 adults (female 447, male 156) aged 20-64 years, and data on socio-economic factors, dietary intake, and dietary habits were obtained by questionnaire interviews. The prevalence of obese individuals was 45.2% among females and 30.1% among males, whereas that of overweight individuals was higher among males than females. Obesity was associated with socio-economic factors for females but not for males. With regard to diet, different patterns between females and males were observed in terms of frequency of food intake, as well as in dietary habits. Our findings of a high prevalence of obese/overweight individuals, together with the characteristics of their diets including changes in the cooking process, suggest that nutrition transition is underway in rural regions as well. Appropriate interventions, therefore, should be introduced to control obesity among women and to enhance health awareness among men throughout the country.