One hundred twenty-four relatives (aged 17-52 years) of 35 children with severe transfusion-dependent beta thalassemia major were investigated for their beta thalassemia carrier status (determined by Hb-A2 level) and iron status (determined by serum ferritin level). Forty-eight males had beta thalassemia trait (BTT) and 18 males did not have BTT (control); 41 females had BTT and 17 females did not have BTT (control). Serum ferritin levels (mean +/- SEM) of male BTT, male control, female BTT, and female control groups were 151.0 +/- 27.4, 59.6 +/- 16.3, 120.6 +/- 36.6, and 17.2 +/- 6.1 mcg/liter respectively; the differences between the two male and the two female groups were statistically significant (p = .05 and p less than .001). Iron deficiency (serum ferritin below 10.0 mcg/liter) was present in 6.3%, 38.9%, 24.4%, and 58.8% of male BTT, male control Female BTT, and female control groups, respectively; the differences between the two male and two female groups were statistically significant (p less than .01 and p less than .01). Serum ferritin was over 1,000 mcg/liter in four individuals with BTT (2 male and 2 female). Thus, the BTT group had better iron nutrition. This may suggest that the BTT group has an advantage in maintaining iron balance.