OBJECTIVE To study the factors influencing the long-term usage of lamivudine (LAM) in chronic hepatitis B (CHB) patients and the management after drug-resistance. METHODS 383 cases of naive CHB patients in our outpatient clinic were treated with lamivudine (100 mg/d) and followed up for at least over 1 year from 2001 to 2010. 129 cases encountered lamivudine-resistance and were then divided into two groups: patients in group A were switched to adefovir dipivoxil (ADV) alternative treatment and those patients in group B were added with ADV for continuous treatment. Efficacy assessment factors included serum HBV markers, HBV DNA, ALT, AFP and other biochemical indicators. RESULTS Among the 383 cases, patients with HBV DNA negative conversion (PCR below test line) at 3 months, 6 months, 1 year, 2 years, 3 years and > 3 years after initial treatment were respectively 156 cases (40.7%), 213 cases (55.6%), 228 cases (59.5% ), 217cases (56.7%), 214 cases (55.9%) and 213 cases (55.6%). HBeAg/HBeAb seroconversion occurred in 62 cases (22.6%). 12 cases were found with primary LAM resistance, 129 cases with HBV breakthrough and rebound, the cumulative resistance rate was 36.8% and the cumulative rebound rate was 34.8%. High baseline viral load, baseline ALT levels < 2 ULN, Lower virologic response rate at week 24 were associated with a higher rebound rate (chi2 is 35.716, 8.728, 43.534, respectively, all with P < 0.01).Viral breakthrough and rebound occurred in 112 patients (86.8%) within 1 year and a half, 123 patients (95.3%) occurred at the end of 2 years and no patient with viral breakthrough and rebound after 5 years. For the patients with viral rebound in group A and group B, the rates of HBV DNA loss were 22.7% (15/66) and 58.7% (37/63) respectively, and the viral response rates were 59.1% (39/66) and 87.3% (52/63) respectively, with chi2 values equaled 17.364 and 12.975 respectively (P < 0.01). CONCLUSIONS For the chronic hepatitis B patients on initial treatment with lamivudine, the viral rebound occurred mainly within 2 years. LAM combined with ADV is more effective than ADV alone for lamivudine-resistant patients.