['Plasma zinc concentration is the preferred biomarker of zinc status, but the time of day and time since previous meals can modify the results. Measuring fasting plasma zinc concentration is not feasible among young children, so adjustments need to be developed for interpreting results. Our objective is to develop correction factors to adjust for the effects of time of day and interval since the previous meal when measuring plasma zinc concentrations of young children.', 'We measured plasma zinc concentrations among young Peruvian (n =297) and Ecuadorian (n=466) children, and constructed regression models adjusting for time of day, interval since previous meal and infections.', 'Plasma zinc concentrations were positively related to the number of hours since the previous meal in the Peru trial (r =0.22, P<0.0001) and negatively related to the time of day of blood sampling in both Peru (r = -0.24, P<0.0001) and Ecuador (r = -0.18, P<0.001). In multivariate models, plasma zinc concentrations were ~2\u2009μg per 100\u2009ml less for each hour later in the morning when blood samples were collected, in both populations, and concentrations were ~1.0\u2009μg per 100\u2009ml greater for every hour since previous meal consumption in Peru. The percentage of children with low plasma zinc concentrations varied according to both these factors.'] Are the time of day and the interval since previous meal associated with plasma zinc concentrations and affect estimated risk of zinc deficiency in young children in Peru and Ecuador?