Interferon-alpha (IFN-α) treatment for chronic hepatitis B (CHB) virus infection is finite and leads to relatively higher functional cure rates (HBsAg loss) than nucleo(s)tide analogue (NA) therapy. Effects of pegylated (PEG)/conventional IFN-α treatment on clinical outcomes were evaluated in an ultra long-term follow-up of CHB patients.HBeAg-positive patients treated with (PEG)IFN-α at a tertiary referral centre between 1977-2014 were included. We reviewed medical charts and consulted the municipal registry for patient information. Patients were invited for a single visit at the outpatient clinic in the case of missing follow-up data. The endpoints included serum HBeAg/HBsAg loss and incidence of clinical events, using life table methods and person-years to analyze the incidence of events. Patients were censored upon retreatment.The study cohort included 267 patients, 67% male, 58% Caucasian, with a median age of 32 years. The median follow-up duration was 11.5 years. The 5 and 10-year cumulative incidence of HBsAg loss were 14% and 32%, respectively. Baseline factors associated with a higher rate of HBsAg loss were male sex, Caucasian race, genotype A, age ≥40 years, and cirrhosis. HBsAg loss rates did not differ significantly between those who received short-term (≤24 weeks) versus long-term (>24 weeks) therapy. Both HBeAg and HBsAg loss were significantly associated with improved clinical outcomes. Early response (HBeAg loss) was associated with more HBsAg loss and better patient outcomes.During long-term follow-up, high rates of HBsAg loss were observed from a single (PEG)IFN-α course. Its persistent effects suggest that a role for IFN-α remains, potentially in novel combination therapies in search of a functional cure.