Many school children in Ethiopia and their mothers are known to be iodine deficient. Prevalence in the Amhara region is around 29%. Micronutrient Initiative, a development organization based in Ottawa, plans to help iodize the salt by providing iodization machines and iodine to the salt producers in Lake Afdira where salt is produced and distributed to the population of Ethiopia. Although it is generally assumed that iodine is important for cognitive development, very few studies examining the effects of iodized salt have been conducted. Studies using a single dose of iodine capsules with children 6 to 12 years showed mixed outcomes with approximately 25% yielding positive outcomes for the intervention children. Sixty districts in Amhara will be randomly selected and randomly assigned so that half receive early delivery of iodized salt. Approximately 6200 mothers and their children 6-, 18-, or 60-months old will be recruited from 1-2 villages in each of the 60 districts, with the help of government-paid Health Extension Workers, for a 12-mo longitudinal study starting in May 2011, prior to the introduction of iodized salt. These same mothers and children will be visited 12 months later for repeated measures. Measures include nutritional status such as height and hemoglobin, along with iodine sufficiency (e.g., goitre, urinary iodine, thyroglobulin), and child development (Bayley Scales of Infant and Toddler Development III, Wechsler Preschool and Primary School Intelligence test for older children). Comparisons will be made within and between groups to determine whether iodized salt has an effect on children's mental development.