We examined serum vitamin B12 and erythrocyte folate concentrations in a representative sample of low and middle income children aged 5–12 y from Bogota's 2006 public schools (n=2811; girls, 49.5%). Mean B12 and folate concentrations were 329 pmol/L (SD, 114; IQR, 249–390) and 848 nmol/L (SD, 246; IQR, 689–970), respectively. As per the IOM cutoff points, the prevalence of B12 deficiency (<150 pmol/L) was 1.8% while the prevalence of marginal deficiency (150–220 pmol/L) was 14.7%. Only 2 children had folate <305 nmol/L. In multivariate analysis, mean B12 concentrations significantly decreased with age (−6 pmol/L per y; 95%CI= −8, −3) and were 16 pmol/L higher in girls than boys (95%CI= 7, 24). B12 was inversely related to the mother's parity and a child's food insecurity index, and positively associated with the household's neighborhood socioeconomic status (SES) classification and the amount of money spent on food per person/day at home. Folate was lowest in children 6–8 y, and among girls, but it was not related to SES or food insecurity. We identified 4 dietary patterns by use of principal components factor analysis of a semiquantitative FFQ (n=951). B12 was positively associated with a pattern that included frequent intake of beef, chicken, and dairy products. Folate was not associated with any specific pattern. Vitamin B12 status is strongly related to SES and intake of animal foods in school children from Bogota. Funded by: Bogota's Secretary of Education, David Rockefeller Center for Latin American Studies at Harvard, Colombian National Institute of Health