Background. Overweight and obesity have reached epidemic proportions in Latin America. Objective. The purpose of this study was to explore social and behavioral factors associated with obesity in Peruvian cities. Design. Between 1998 and 2000 health examination surveys were conducted among adults in 1176 families identified in six cities. Stratified by social class, multistaged random sampling was used. Using body mass index (weight (kg)/height (M)(2)), men and women were classified into normal weight (BMI < 25), overweight (BMI 25-29), or obese (BMI greater than or equal to 30); abdominal circumference (greater than or equal to 94 cm in men and 84 cm in women) further identified morbidity risk. Several demographic, social, and behavioral variables were collected following standardized procedures. Results. Adjusting for age, 37% of women were categorized as normal weight, 40% overweight, and 23% obese; corresponding figures for men were 40, 44, and 16%. More developed cities, e.g., Lima, Arequipa, and Ica, had the largest prevalence of overweight and obesity for both men and women. Adjusted logistic models showed that BMI greater than or equal to 25 was positively correlated with age; whereas, education was negatively associated, only among women. Other significant associated factors of overweight included city of residence, television viewing :4 h daily in women, and underestimation of body weight status. Conclusions. The study showed elevated rates of overweight across the income level spectrum. Factors such as urban development stage, income, education, and gender posed differential relationships with the risk of overweight and must be considered in designing future public health interventions. Underestimation of body weight status and sedentary behavior may also constitute specific areas of intervention. (C) 2003 American Health Foundation and Elsevier Inc. All rights reserved.