Background: Few studies with diverging results and a small sample size have compared autoimmune hepatitis (AIH) in the elderly to younger patients. Aim: To unbiasedly investigate the role of age in behaviour and treatment outcome of AIH. Methods: All patients with probable or definite AIH type 1 in four tertiary academic centres were included in this retrospective - and since 2006 prospective - cohort study. Influence of age on presentation, remission and outcome of AIH were investigated. Results: 359 patients were included. Presence of cirrhosis at AIH diagnosis around 30% was independent of age. ALAT was higher at age 30-60 years on AIH diagnosis, and above age 60 there were less acute onset, less jaundice and more concurrent autoimmune disease. Remission was reached in 80.2%, incomplete remission in 18.7%, only 1.1% (all aged 50-65) was treatment-refractory. Age was not an independent predictor of remission, while cirrhosis was. Above age 45 there was more diabetes, above age 60 more loss of remission. Rate of progression to cirrhosis was 10% in the 10 years after diagnosis and unrelated to age at AIH diagnosis. With onset below age 30, there was more development of decompensated cirrhosis over time. With higher age at AIH diagnosis there was a lower survival free of liver-related death or liver transplantation. Conclusions: AIH presents at all ages. Age influences features at diagnosis, but not response to treatment, while survival without liver-related death or liver transplantation decreases with higher age at diagnosis.