Fluorimetric determination of selenium in colostrum, transitional and mature human milk gave the following concentrations (mean and standard deviation): 41 ± 16, 23 ± 6 and 17 ± 3 ng Se ml-1, respectively. The ranges for each kind of milk, especially for mature milk, were narrow. For all cases studied, the Se concentration in milk decreased with lactation time, reaching a plateau, at 17 ng Se ml-1, after 20 days. It is estimated that breast-fed-only babies in Greece receive ∼ 5-11 μm Se day-1 up to 6 month of age. From consumed food data it was estimated that adult Greeks receive 100 ± 6 μg Se day-1, in close agreement with our previously determined value of 110 μg Se day-1 estimated from food disappearance data.