Background & Aims: Patients with hepatitis B e antigen (HBeAg)-negative chronic hepatitis B treated with peginterferon alfa-2a with or without lamivudine achieve significantly higher 6-month posttreatment rates of response compared with those treated with lamivudine alone. The durability of <= 3-year posttreatment response was investigated in this study. Methods: Patients received peginterferon alfa-2a only (180 p,g once weekly; n = 177), in combination with lamivudine (100 mg daily; n = 179) or lamivudine alone (n = 181) for 48 weeks. A total of 315 patients (116, 114, and 85, respectively) participated in this posttreatment observational study. Results: Three years after treatment, the percentage of patients with normal alanine aminotransferase (ATL) was higher for patients treated with peginterferon alfa-2a (31%) than with lamivudine (18%; P = 0.032). Similarly, 28% of patients treated with peginterferon had hepatitis B virus (HBV) DNA levels 10,000 copies/mL versus 15% of patients treated with lamivudine (P = .039). Peginterferon alfa-2a treatment and high baseline ALT level were independent baseline predictors of long-term virologic response (P = .040 and P = .01, respectively). Of the patients who had been treated with a peginterferon alfa-2a-containing regimen, 8.7% cleared hepatitis B surface antigen (HBsAg; 44% of those with undetectable HBV at 3-year posttreatment follow-up) compared with none treated with lamivudine alone. Conclusions: Biochemical and virologic responses were sustained for 53 years in approximately 25% of patients given a 48-week course of peginterferon alfa-2a, with or without lamivudine. The increased rate of HBsAg clearance in patients with HBeAg-negative chronic hepatitis B supports the use of peginterferon alfa-2a as a first-line treatment.