The objective of this study was to determine the prevalence of iron deficiency with and without anemia in a convenience sample of trained male and female adults. One hundred twenty-one adults (72 female, 49 male) involved in aerobic training (11.2+/-6.3 hr/wk for >/=6 consecutive months), ages 18 to 41 years old, participated in an iron status screening. The concentrations of hemoglobin (Hb), ferritin, and transferrin receptor were measured in serum to determine the prevalence of iron deficiency with and without anemia. Eight individuals (seven female, one male) had iron deficiency with anemia (serum ferritin <16 microg/L; Hb<120 g/L female, <136 g/L male). Iron deficiency without anemia (serum ferritin </=16 microg/L) was found in 29% of female and 4% of male subjects. Determination of iron deficiency without anemia using the transferrin receptor-ferritin index (serum transferrin receptor:log serum ferritin>/=4.5) found 36% of female and 6% of male subjects to be iron deficient without anemia. Recreational athletes should be screened for iron deficiency without anemia using serum ferritin, serum transferrin receptor, and Hb.