This study is designed to evaluate the effectiveness, safety, and tolerability of tenofovir DF monotherapy versus emtricitabine (FTC)/tenofovir DF combination therapy in participants with chronic HBV with lamivudine resistance (presence of the rtM204I/V mutation with or without the rtL180M mutation) over a 240-week period. Participants in this study must be receiving lamivudine treatment at the time of enrollment.