A community-based, cross-sectional survey was conducted in the South Island of New Zealand to assess the dietary and biochemical selenium status of children (n = 136) and their mothers (n = 302), and to assess factors influencing selenium status. Serum and plasma samples from children and their mothers were analyzed for selenium using graphite furnace atomic absorption spectrometry. Dietary selenium intakes were analyzed from 3-d weighed diet records, and food sources of selenium were quantified. Mean dietary selenium intakes in infants (6-11.9 mo), toddlers (12-24 mo), and mothers were below recommended levels. Toddlers had higher selenium intakes than infants (13.7 +/- 8.4 and 7.9 +/- 6.2 microg/d, respectively, P = 0.0001) and the selenium density of their diets was also higher [3.2 +/- 1.7 and 2.4 +/- 1.7 microg/(MJ . d), respectively, P = 0.003]. Household smoking was associated with lower serum selenium concentrations in infants and toddlers (P = 0.02). South Island women who were currently pregnant had lower plasma selenium concentrations (0.74 +/- 0.15 micromol/L) than nonpregnant lactating and nonpregnant nonlactating women (0.94 +/- 0.16 and 0.93 +/- 0.16 micromol/L, respectively, P = 0.0001). Clearly, pregnant women, infants and toddlers are at risk of suboptimal selenium status, and further research is warranted to assess potential effects in these groups. The finding of an association between household smoking and lower selenium concentrations in children should be investigated further. Dietary interventions are recommended to improve dietary selenium intakes in South Island children and their mothers.