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Low folate concentrations are inversely associated with birth defects, including neural tube defects, congenital heart disease and oral clefts. Conversely, high folate concentrations may be associated with adverse outcomes, including increased risk of colorectal cancer among those with pre-existing neoplasms. The purpose of our study was to investigate the folate status of a nationally representative sample of Canadians, including a subset of women of childbearing age.We examined red blood cell folate concentrations among members of the general population aged 6-79 years (n = 5248) and separately among women of childbearing age (15-45 yr, n = 1162), as recorded by the Canadian Health Measures Survey and measured by immunologic assay. We assessed the data for significant differences by age, sex and socioeconomic status.Less than 1% of Canadians showed folate deficiency (red blood cell folate305 nmol/L) and 40% showed high folate concentrations (1360 nmol/L). Among women of childbearing age, 22% showed concentrations below those considered optimal for maximal neural tube defect-risk reduction (906 nmol/L). Significant differences by age and socio-economic status, but not sex, were evident in median red blood cell folate concentrations, although concentrations in all groups exceeded recommended levels. No differences by age or income were found among women of child-bearing age.Folate deficiency is virtually nonexistent in the Canadian population, although high folate concentrations are evident. Additional research is needed to better understand the determinants of red blood cell folate among women of childbearing age who have concentrations below levels that are maximally protective against neural tube defects. Ongoing monitoring of the folate status of Canadians and the relationship between red blood cell folate and health outcomes is warranted.