In brief: The incidence of anemia, based on hemoglobin concentration, is reported to be higher in adolescent boys than in girls. The authors tested 437 adolescents for anemia and found that if Hct alone was used to diagnose anemia, it is present in 2 1/2 times more boys than girls. If Hct and percentage of transferrin saturation were used, 1.6 times as many boys as girls were anemic. More adolescent boys, particularly those in the growth spurt, are anemic than are adolescent girls, but more girls than boys with deficient iron stores are nonanemic. In general, physicians should be less concerned about boys with low Hct and more concerned with adolescent girls with normal Hct.