en General پژوهشي Research Article Background: Hepatitis B is a serious liver infection and one of the 5 leading causes of death around the world. Chronic hepatitis B has a variant natural history. Around one-third of patients with chronic hepatitis may eventually develop cirrhosis or hepatocellular carcinoma. The aim of this study was to follow-up chronic hepatitis B carriers. Methods: This cross-sectional descriptive-analytical study was done on 235 chronic hepatitis B carriers, who referred to an infectious disease and tropical medicine clinic, in Birjand, Iran. All chronic hepatitis B carriers, who had referred to the study settings from 2005 to 2013, were approached. Data were entered in the SPSS software (v. 21.0) and analyzed via the Chi-square and the Fisher’s exact tests at a significance level of less than 0.5. Results: The majority of participants were male (132 cases, 56.2%) and married (193 cases, 82.1%) and were aged 33.3 ± 0.7. The follow-up mean time was 5 years with a range of 3 to 9 years. During this follow-up period, 10 individuals (4%) experienced seroconversion from hepatitis B surface antigen (HBsAg) positivity to negativity, 35 (15%) developed active hepatitis, 8 (3.5%) developed cirrhosis, and 2 (1%) developed liver cancer. The remaining 180 participants (76.5%) had inactive hepatitis. Among participants, 45 (19%) were hepatitis B e antigen-positive, 24.5% of whom experienced positivity to negativity seroconversion. Conclusions: Most chronic hepatitis B carriers are primarily asymptomatic. However, 15% developed serious liver disease over time. Therefore, careful lifelong follow-up assessments are needed for early diagnosis and prevention. Natural History,Chronic Hepatitis B,Hepatitis B Carriers 0 0 http://mcj.bums.ac.ir/browse.php?a_code=A-10-1-51&slc_lang=en&sid=1 Tahereh Darvishpoor Kakhki 10031947532846003508 10031947532846003508 No Ophthalmologist Resident, Shahid Beheshti University of Medical Sciences, Tehran, Iran Bita Bigari 10031947532846003509 10031947532846003509 No Infectious Disease Research Center, Birjand University of Medical Sciences, Birjand, Iran Ghodsiyeh Azarkar 10031947532846003510 10031947532846003510 No Infectious Disease Research Center, Birjand University of Medical Sciences, Birjand, Iran Masood Ziaee 10031947532846003511 10031947532846003511 Yes Masood Ziaee, Infectious Diseases Research Center, Birjand University of Medical Sciences, Birjand, Iran. Tel: +98-9151613942, Fax: +98-5632433004, E-mail: dr.m.ziaee@gmail.com