GROUP A: Patients with HBeAg (+) or HBeAg (-) compensated chronic hepatitis B who did not discontinue treatment in their previous study due to an efficacy response and required further treatment or who had met the criteria for discontinuation of treatment in their previous study due to efficacy, but were being maintained on study drug by the principal investigator. For patients treated with telbivudine who enrolled into Group A from studies 2302 and 015, the total telbivudine treatment time (starting from feeder study baseline to the end of the on-treatment period in study 2303) was 208 weeks. For patients treated with lamivudine in studies 2302/015 and enrolled into group A and for all patients in group A from studies 2401/2402/010, the total telbivudine treatment time was 104 weeks.