According to the German Nutrition Survey 1998 (GeNuS), the intake of folate is rather low. Since periconceptional folic acid supplementation may prevent neural tube defects, but less than 10% of pregnant women follow this recommendation, a folic acid fortification of flour is currently considered. The impact of different fortification measures on folate intake of adults is analysed. Dietary data of the 4030 GeNuS participants, ages 18-79 years, were analysed allowing for different flour fortification levels (100, 150, and 200 Āµg folic acid per 100 g flour) as well as two possible levels of folic acid fortification of milk products, soft drinks and cereals. The folic acid contents and sale proportions of these foods were determined in a market study. The obtained folic acid contents of these foods and virtual flour fortifications were implemented in the German Food Code and Nutrient Data Base and connected with food intake data of GeNuS. A low fortification level of the three food groups and an additional flour fortification with 100 Āµg folic acid reduces the population part with an intake below the reference value of 400 Āµg /d folate equivalents from 72-92% to about 5-27% (depending on age and gender). After doubling the flour fortification to 200 Āµg folic acid, less than 0,5% of the population exceeds the tolerable upper intake level of 1 mg/day folic acid. A high fortification level of the three food groups, however, increases this proportion to 3-5%. A folic acid fortification of flour will improve the population's folate intake, without increasing the risk of exceeding the tolerable upper intake level of folic acid for most persons. This measure gives better controllable folic acid intake levels than the uncoordinated fortification of processed foods.