BACKGROUND: Azathioprine (AZA) and mercaptopurine (MP) are the cornerstone of steroid-sparing strategies in autoimmune hepatitis (AIH). Up to 20% of patients do not tolerate or respond to these regimens. AIM: To evaluate retrospectively the tolerability and efficacy of tioguanine (thioguanine) (TG) therapy in selected patients with AIH and AIH variant syndromes. METHODS: Records of 52 patients who received TG therapy were retrieved from nine hospitals in the Netherlands. Indications for TG treatment were intolerable side effects on AZA or MP (n = 38), insufficient response (n = 11) or first-line treatment (n = 3). Treatment efficacy was defined as normalisation of serum aminotransferases and serum immunoglobulin G. RESULTS: No serious adverse events occurred in patients treated with TG during a median follow-up of 18 months (range 1-194). Treatment was well tolerated in 41 patients (79%), whereas four had tolerable (8%) and seven (13%) intolerable side effects. Thirty-eight patients were treated with TG after intolerable side effects on AZA or MP; 29 patients continued TG therapy of whom 24 (83%) achieved complete biochemical remission, four (14%) had incomplete and one (3%) had no response; nine discontinued treatment. Seven of 11 patients with insufficient response to AZA or MP were responsive to TG, three with complete and four with incomplete biochemical remission; four discontinued due to intolerance (n = 2) and non-response (n = 2). TG was effective in all AIH patients as first-line maintenance treatment. CONCLUSION: In our retrospective review of TG therapy in selected patients with AIH or AIH variants who previously failed on AZA or MP, TG appeared tolerable with biochemical efficacy.