Anemia is a significant public health problem in Vietnam, but representative national data and comprehensive risk factors analysis are lacking. The objectives of this study were to: 1) determine the distribution and severity of anemia in Vietnam, and 2) to assess potential risk factors for anemia. Nine thousand five hundred fifty households in 53 provinces were covered using a stratified two-stage cluster survey carried out in 1995. Selected household members were interviewed; intestinal helminthes were tested in non-pregnant women by Kato-Katz technique; hemoglobin concentrations were measured with Hemocue. Data were weighted and analyzed by survey procedures using SAS 9.0. Overall, 60% of children under 2 years old, 53% of pregnant women, 40% of non-pregnant women and 15.6% of men were anemic. Hookworm infection was the strongest factor associated with anemia (OR = 1.7; 2.9 and 4.5 for 11,999, 2,000-3,999 and > or = 4,000 hookworm egg counts, respectively) and accounted for 22% of anemia. Hookworm intensity was significantly associated with hemoglobin level; for each 1,000 egg increase, hemoglobin was reduced by 2.4 g/l. Living in different ecological zones, eating < 1 serving of meat/ week, and farming were significantly associated with anemia in women and children. Other risk factors in women included having > 3 children and having a child < 24 months old. In men, no variables were found significantly associated with anemia.