Several recent reports have found a high prevalence of vitamin D deficiency in the adult British population. The present paper investigates the associations of low income/material deprivation and other predictors of serum 25-hydroxyvitamin D (25(OH)D) status in two surveys: The National Diet and Nutrition Survey (NDNS) of the population aged 19-64 years in mainland Britain and the Low Income Diet and Nutrition Survey (LIDNS) of adults aged > or = 19 years in all regions of the UK who were screened to identify low-income/materially deprived households. A valid serum 25(OH)D sample was obtained in 1297 and 792 participants from the NDNS and LDNS respectively. The NDNS participants who were not receiving benefits (n 1054) had a mean 25(OH)D of 50.1 nmol/l, which was higher than among NDNS participants receiving benefits (n 243) with a mean 25(OH)D of 43.0 nmol/l (P < 0.001) and the LIDNS sample (46.5 nmol/l; P < 0.05). For all three samples, the season of drawing blood, skin colour, dietary intake of vitamin D, and intake of dietary supplements were significant predictors (P < 0.05) of serum 25(OH)D status in mutually adjusted regression models. National prevention and treatments strategies of poor vitamin D status need to be targeted to include the adult population, particularly deprived populations, in addition to the elderly and ethnic minorities.