Obesity is a worldwide public health problem impacting not only industrialized nations but also developing countries. The main objective of this paper was to analyze risk factors for overweight among Amerindian children and their mothers. Data were collected in 15 Amerindian riverside communities from the Beni River (Bolivia). The total sample was of 195 mothers and 452 children, 0-15 years of age. Information about family activity and dietary patterns was collected, and a clinical examination was performed. Stool samples were collected in children for parasitological screening. Anthropometric measurements, including weight, height, arm circumference, and four skinfolds, were taken. A bioelectrical impedance analysis was performed in mothers. In total, 12.2% (95% confidence interval (CI(95%)) 9.1-15.9%) of the children were considered overweight; less than 1% were overtly obese International Obesity Task Force (IOTF) criteria. Among their mothers, 35.3% (CI(95%), 28.7-42.5%) were overweight (BMI (weight/height (2)) >25 kg/m(2)), and 5% (CI(95%), 2.5-5.1%) were obese (BMI >30 kg/m(2)). BMI was moderately related to anthropometric indices of body composition in children, but was highly correlated with fatness in mothers. The risk of overweight was not associated with environmental factors in children. In mothers, there was a significant relationship between BMI, health status, and dietary diversity score. There was a moderate association in boys between fatness and the BMI of their mothers (R(2) = 0.12, P < 0.001), but not in girls. These findings suggest a trend toward accumulation of fat related to possible changes at the economic and agricultural levels, even in remote rural areas.