OBJECTIVE: To evaluate the prevalence and characteristics of anemia in the long distance runners. METHOD: Subjects included 61 long distance runners and 40 control. The 61 subjects averaged 39.9+/-4.5 years of age. Long distance runners has been training for at least 6 months. Hemoglobin, iron, total iron binding capacity, reticulocyte count, peripheral blood smear, urine hemosiderin were evaluated. WHO criteria cut off value of hemoglobin for the diagnosis of anemia was used, 13 g/dl in men and 12 g/dl in women. Iron deficiency was defined as the percent transferrin saturation less than 15. The percent transferrin saturation was calculated by dividing the serum iron level by the total iron-binding capacity. RESULTS: Anemia occurred in only 2.0% and 9.0% of the male and female long distance runners respectively and other laboratory findings supported diagnosis of iron deficiency anemia. The percentage of iron deficiency anemia was lower than normal control. Iron deficiency was evident in 6.0% and 18.1% of the male and female long distance runners respectively. CONCLUSION: Recreational long distance runners were at no greater risk for developing a frank anemia than the non-exercising population.