GROUP C: Patients with either compensated or decompensated chronic hepatitis B, who had discontinued study drug treatment in their previous Idenix-sponsored study due to an efficacy response as recommended by protocol. Patients who were eligible for treatment discontinuation in their previous study but who were, at the principal investigators discretion, continued on study therapy, were eligible to enter this study in Group C provided their treatment was discontinued at their last visit of the previous study. The feeder studies for group C of current study were study 2302/015, 2401, 2402, and 010. For patients who enrolled into group C, total telbivudine treatment time was 104 weeks starting from the baseline of the feeder studies to their last visit of the feeder studies. Patients were enrolled to current study (study 2303) for off-treatment follow-up after the treatment discontinuation due to efficacy. Hence, patients did not receive any study drug except in case of patients who relapsed and reinitiated treatment.