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Background and Objective: Hepatitis B vaccination has been conducted in neonates in the routine vaccination in Iran since 1993. This study was carried out to evaluate the serum hepatitis B antibody level in vaccinated children after 14 years in Kashan, Iran. Materials and Methods: This prospetive cohort study was conducted on 200 fourteen-year-old children which were selected via a simple random sampling method in Kashan, Iran drung 2008-09. This subjects were have been vaccined according to the govermental guildline at 0, 2 and 6 months old. Two ml blood specimens were obtained from children and serum hepatitis B surface antibody (anti-HBs) and hepatitis B core antibody (anti-HBc) were determined by ELISA method. Immunity was interpreted as anti-HBs≥10 IU/L. Data were analyzed using SPSS-13, Chi-Square and Fisher’s exat tests. Results: 92% girls and 95% boys, totally 187(93.5%) children had serum anti-HBs≥10 IU/L. Anti-HBc was positive in 3 (3%) girls and 5(5%) boys, totally 8(4%) which all of them had serum anti-HBS≤10 IU/L. No case of positive HBs Ag was detected. Immunity was detected in 11 of 18 (61.1%) children with birth weight<2.5 kg and in 176 of 182 (96.7%) children with birth weight≥2.5 kg (P<0.05). Conclusion: The immunity following the complete series (0, 2, 6 months old) of hepatitis B vaccination remained detectable after 14 years.