Background and purpose: Detection of beta thalassemia carriers, for the genetic consultation and prevention of thalassemic birth cases is very important. Rate of hemoglobin A2 is the base for diagnosis. It is believed that coincidence of iron deficiency anemia with beta thalassemia would lead to nonproduction of hemoglobin A2, as a result, would mask diagnosis of beta thalassemia. Hence in a nation wide plan on screening of microcytic and hypochromic marital candidates with normal HbA2, ferrous sulfate is prescribed for one month, and followed by the second examinatin. Cases and the results of this intervention is not reported. This study was conducted in order to determine the effect of ferrous sulfate on the diagnosis of minor beta thalassemia in 1998 and 1999.Materials and methods: This study was an open clinical trial done on two groups of patients. First group comprised the mothers of confirmed minor thalassemic patients, referring to Boali hospital for iron deficiency anemia, due to gender, and Socio- economic conditions Iron deficiency was probable in them. The second group, included the patients with confirmed microcytosis HCV<80FL done in province health center, but with normal HbA2 (HbA2<3.5%). All the patients in both groups were given two tablets of ferrous sulfate per day for one month. CBC, curpuscular indices, HbA2, Ferritin, SL, TIB, iron before and after intervension were measured. The one with SI≤16% and/or ferritin ≤15 mg/ml was called iron defficieny anemia. Paired T- test was used for the comparative analysis of the data obtained before and after intervension.Results: First group comprised of, 27 females with mean age of 36 years suffering from thalassemia minor,all of them with HbA2 above 3.5%(5.5+71%) and 8(4%) patients had iron deficieny anemia. Before intervension they had HbA2 above diagnostic level. Even those suffering from iron deficiency anemia the changes in the rate of iron before and after intervension were not obvious. The second group comprised of 19 patients, 12 men and 8 women with mean age of 20.8 years, from this number of patients, 9 persons suffered from iron deficiency and inspite of using ferrous sulfate, the rate of A2 hemoglobin could not change in all patients of the group (before 2.9% ± 0.3% and after 2.9%±0.2%). Changes in the rate of iron were the indication for iron consumption.Conclusion: Iron consumption would not cause a significant change in HbA2. A nation wide reports and data concerning anemia is recommended to be collected, analyzed and published.