Assessment of the quality of donor selection and safety of the blood supply can be estimated by monitoring the prevalence of the serologic markers of infectious disease in screening tests. In the present study, changes in rates of hepatitis B virus (HBV) infection are studied in the period 1998-2007 in Iranian Blood Transfusion Organization (IBTO). Prevalence of serological marker of HBV infection [hepatitis B surface antigen (HBsAg)] was evaluated in blood donations in Iran as well as for Fars province representing a low prevalence, and Sistan-Baluchestan (S&B) province as a high prevalence region throughout 1998-2007. For assessing frequency of infection, the prevalence of HBsAg per 100 000 donations and 95% confidential intervals (95% CIs) is calculated. P value is estimated by chi(2) test. A total of 14 599 783 donations were collected during 10 years. The overall HBsAg prevalence rates declined from a 1.79% (1789/100 000 donations) in 1998 to 0.41% (409/100 000 donations) in 2007 in Iran. In Fars province, HBsAg prevalence decreased from 0.89% in 92 999 donations in 1998 to 0.34% in 148 014 donations in 2007 and in S&B province, the rate of HBsAg has gone down from 3.74% in 44 036 donations in 1998 to 1.15% in 56 057 donations in 2007. The frequency of HBV infection entering the blood supply has decreased over this period as a result of improvement in donor recruitment and selection, usage of software in transfusion services and possibly decreasing HBV infection prevalence in general population.