BACKGROUND: Ulcerative colitis (UC) occurring during childhood is generally extensive and is associated with severe flares that may require intravenous steroid treatment. In cases of corticosteroid resistance is necessary to introduce a second-line treatment to avoid or delay surgery. AIMS: To describe the efficacy and safety of oral tacrolimus for the treatment of severe steroid-resistant UC. METHODS: We performed a retrospective study that included all patients under age 18 suffering from severe steroid-resistant UC treated with oral tacrolimus during the period January 1998 to October 2012 and with a follow-up period after treatment of 24months or more. RESULTS: A total of ten patients were included. The age at baseline was 9.4±4.9years, and the time from diagnosis was 1.3months (IQR, 1-5.7). Seven of the patients were in their first flare of disease. All of them received an oral dose of 0.12mg/kg/day of tacrolimus divided in two doses. Trough plasma levels of tacrolimus were maintained between 4 and 13ng/ml. Response was seen in 5/10 patients at 12months, colectomy was eventually performed in 60% of patients during the follow-up period. CONCLUSIONS: Tacrolimus is useful in inducing remission in patients with severe steroid-resistant UC, preventing or delaying colectomy, and allowing the patient and family to prepare for a probable surgery. Tacrolimus may also be used as a treatment bridge for corticosteroid-dependent patients until the new maintenance therapy takes effect.