The primary aim of this study was to assess the biochemical vitamin B12 and folate status of a representative group of elderly women (70-80 y) living in Dunedin, New Zealand. A second aim was to determine the prevalence of hyperhomocysteinaemia and to explore the determinants of homocysteine (hcy) concentration in this population. A cross-sectional study was carried out between June and August of 2000. Two hundred and fifty women were randomly selected from the 1998 electoral roll. Fasting blood samples were analysed for folate, vitamin B12, total hcy, creatinine, and haematological parameters. Of the women selected, 87 did not respond, 37 were not traceable, 23 were not eligible or had died, and 103 agreed to participate. The overall response rate was 46%. Based on a cut-off of 150 pmol/L for serum B12, 13% of participants would be classified as having sub-optimal vitamin B12 status. Of the women, 3 and 5%, respectively, had low serum (< 6.6 nmol/L) and erythrocyte folate (< 317 nmol/L) concentrations. No participant had megaloblastic anaemia. The prevalence of hyperhomocysteinaemia (> 15 mumol/L) in this population was 18%. Hyperhomocysteinaemia in this group may be partly explained by renal insufficiency because there was a significant association between serum creatinine and plasma hcy (P < 0.001). Blood folate levels but not serum B12 were significantly inversely associated with hcy. In conclusion, there was a moderately high prevalence of hyperhomocysteinaemia and suboptimal plasma vitamin B12 concentrations but not low blood folate concentrations in this elderly female population.