['To assess whether persistent micronutrient deficiencies in Mongolian children identified in our earlier biochemical study are associated with inadequacies in quantity and/or quality in their complementary diets.', 'A cross-sectional study of breast-fed children aged 6-23 months, randomly selected from four districts in Ulaanbaatar and four provincial capitals.', 'Weight and length were measured, and sociodemographic status, feeding practices and nutrient adequacy of complementary foods for children aged 6-8 months (n 26), 9-11 months (n 29) and 12-23 months (n 73) were assessed via questionnaire and in-home interactive 24 h recalls.', 'No geographic differences existed so data were combined. Adherence to WHO infant and young child feeding practices was poor: few children were exclusively breast-fed up to 6 months of age or received the recommended number of feedings containing the recommended number of food groups. Nevertheless, energy intakes from complementary diets, primarily from cereals and non-nutritious snacks, were above WHO-estimated needs; <1 % of energy was from meat and eggs or fruits and vegetables. Median intakes and densities of most nutrients (except protein, thiamin and riboflavin) failed to meet WHO recommendations for at least two age groups, assuming average breast milk intake; greatest density deficits were for Fe > vitamin C > vitamin A > Zn > Ca.'] Is poor dietary quality of complementary foods associated with multiple micronutrient deficiencies during early childhood in Mongolia?