Aleurone flour (ALF) is a rich source of natural folate (>500 microg/100 g wet weight). Our objective was to establish whether intake of ALF in man can significantly improve folate status and reduce plasma homocyst(e)ine. We performed a randomised, controlled intervention, of 16 weeks duration, in free-living healthy individuals (mean age 46-52 years). Participants were assigned to one of three groups: ALF, 175 g bread made with ALF and placebo tablet each day; PCS, 175 g bread made with pericarp seed coat (PCS) flour and placebo tablet each day (low-folate control); or FA, 175 g bread made with PCS flour and tablet containing 640 microg folic acid each day (high-folate control). The daily folate intake contributed by the bread and tablet was 233 microg in the PCS group, 615 microg in the ALF group and 819 microg in the FA group. The number of participants completing all phases of the PCS, ALF and FA interventions was twenty-five, twenty-five and eighteen, respectively. Plasma and red-cell folate increased significantly (P<0.0001) and plasma homocyst(e)ine decreased significantly (P<0.0001) in the ALF and FA groups only. Plasma folate and red-cell folate in the ALF group (mean, 95 % CI) increased from baseline values of 12.9 (9.9, 15.7) nmol/l and 509 (434, 584) nmol/l to 27.1 (22.5, 31.7) nmol/l and 768 (676, 860) nmol/l, respectively. Plasma homocyst(e)ine in the ALF group decreased from 9.1 (8.2, 10.0) micromol/l at baseline to 6.8 (6.2, 7.5) micromol/l after 16 weeks. In conclusion, moderate dietary intake of ALF can increase red-cell folate and decrease plasma homocyst(e)ine substantially.