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.Patients received peginterferon alfa-2a only (180 μg 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.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.Biochemical and virologic responses were sustained for ≤3 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.