AIM: To assess the effectiveness and side-effects of lamivudine therapy for children with chronic hepatitis B (CHB) who fail to respond to or have contraindications to interferon-α(IFN-α) therapy. METHODS: Fifty-nine children with CHB were treated with 100 mg lamivudine tablets given orally once daily for 12 mo. Alanine aminotransferase (ALT) activity was evaluated monthly during the therapy and every 3 months after its discontinuation. HBe antigen, anti-HBe antibodies, HBV DNA level in serum were evaluated at baseline and every six months during and after the lamivudine therapy. Sustained viral response (SVR) to lamivudine therapy was defined as permanent (not shorter than 6 mo after the end of the therapy), namely ALT activity normalization, seroconversion of HBeAg to anti-HBe antibodies, and undetectable viral HBV-DNA in serum (lower than 200 copies per mL). The analysis of the side-effects of the lamivudine treatment was based upon interviews with the patients and their parents using a questionnaire concerning subjective and objective symptoms, clinical examinations, and laboratory tests performed during clinical visits monthly during the therapy, and every 3 mo after the therapy. RESULTS: ALT normalisation occurred in 47 (79.7%) patients between the first and 11th mo of treatment (mean 4.4±2.95 mo, median 4.0 mo), and in 18 (30.5%) of them after 2 mo of the therapy. There was no correlation between the time of ALT normalization and the children’s age, the age of HBV infection, the duration of HBV infection, inflammation activity score (grading), staging, ALT activity before treatment, serum HBV DNA level, and lamivudnie dose per kg of body weight. HBeAg/anti HBe seroconversion was achieved in 27.1% of cases. The higher rate of seroconversion was connected with lower serum HBV DNA level and longer duration of HBV infection. There was no connection between HBeAg/ anti HBeAb seroconversion and the children’s age, age of HBV infection, grading, staging, ALT activity before treatment, and lamivudnie dose per kg of body weight. No complaints or clinical symptoms were observed during lamivudine therapy. Impairment of renal function or myelotoxic effect was noted in none of the patients. CONCLUSION: One year lamivudine therapy for children with chronic hepatitis B is effective and well tolerated. Seroconversion of HBeAg/HBeAb and SVR are connected with lower pre-treatment serum HBV DNA level. AIM: To assess the effectiveness and side-effects of lamivudine therapy for children with chronic hepatitis B (CHB) who fail to respond to or have contraindications to interferon-α (IFN-α) therapy. METHODS: Fifty-nine children with CHB were treated with 100 mg of lamivudine tablets given orally once daily for 12 mo. Alanine aminotransferase (ALT) activity was evaluated monthly during the therapy and every 3 months after its discontinuation. HBe antigen, anti-HBe antibodies, HBV DNA level in serum were evaluated at baseline and every six months during and after the lamivudine therapy. Sustained viral response (SVR) to lamivudine therapy was defined as permanent (not less than 6 mo after the end of the therapy), namely ALT activity normalization, seroconversion of HBeAg to anti- HBe antibodies, and undetectable viral HBV-DNA in serum (lower than 200 copies per mL). The analysis of the side-effects of the lamivudine treatment was based upon interviews with the patients and their parents u sing a questionnaire concerning subjective and objective symptoms, clinical examinations, and laboratory tests performed during clinical visits monthly during the therapy, and every 3 months after the therapy. RESULTS: ALT normalization occurred in 47 (79.7%) patients between the first and 11th mo of treatment (mean 4.4 ± 2.95 mo, median 4.0 mo), and in 18 (30.5%) of them after 2 mo of the therapy. There was no correlation between the time of ALT normalization and the children’s age, the age of HBV infection , the duration of HBV infection, inflammation activity score (grading), staging, ALT activity before treatment, serum HBV DNA level, and lamivudnie dose per kg of body weight. HBeAg / anti HBe seroconversion was achieved in 27.1% of cases. rate of seroconversion was connected with lower serum HBV DNA level and longer duration of HBV infection. There was no connection between HBeAg / anti HBeAb seroconversion and the children’s age, age of HBV infection, grading, staging, ALT acti vity before treatment, and lamivudnie dose per kg of body weight. No complaints or clinical symptoms were observed during lamivudine therapy. Impairment of renal function or myelotoxic effect was noted in none of the patients. CONCLUSION: One year lamivudine therapy for children with chronic hepatitis B is effective and well tolerated. Seroconversion of HBeAg / HBeAb and SVR are connected with lower pre-treatment serum HBV DNA level.