INTRODUCTION: Budesonide MMX((R)) is approved for induction of remission in mild-to-moderate active ulcerative colitis (UC) in adults in whom 5-ASA is not sufficient. There is a lack of data on its effectiveness and safety in clinical practice. MATERIAL AND METHODS: The CORE Practice study was a multi-centre prospective, observational study of mild-to-moderate UC-patients treated with Budesonide MMX((R)) 9 mg for up to 8 weeks (induction). Enrolled patients had previously been prescribed Budesonide MMX((R)) 9 mg in accordance with the SmPC within a 5-day time window. The primary endpoint was the percentage of patients achieving a decrease >/= 3 points in the UCDAI clinical sub-score at the end of the induction treatment. Other endpoints were clinical remission (decrease </= 1 in UCDAI clinical sub-score), resolution of symptoms, change in Short Inflammatory Bowel Disease Questionnaire (SIBD-Q) score, treatment satisfaction, and tolerability. This report presents results from the Polish study sites. RESULTS: The data from a Polish subgroup of 181 patients with mild-to-moderate UC were analysed. Clinical improvement >/= 3 points in the UCDAI at the end of treatment induction was achieved in 63.8% patients. Clinical remission was observed in 55.9% of patients at the end of the induction treatment. Full resolution of symptoms (rectal bleeding = 0 and stool frequency = 0) at the end of the Budesonide MMX((R)) treatment was achieved in 52.5% of patients. Significant improvement in quality of life was seen in mean SIBD-Q total score from 40 points at baseline to 56 points at last assessment (p < 0.001). A treatment satisfaction score of more than 8 out of 10 was observed in 72.9% of patients. One patient discontinued Budesonide MMX((R)) due to an adverse event that was related to the study drug, which counted for less than 1% of patients. CONCLUSIONS: The data from the Polish subgroup of the real-life study CORE Practice confirms the clinical efficacy of Budesonide MMX((R)) 9 mg in the majority of patients with active mild-to-moderate UC. Budesonide MMX((R)) was safe and well tolerated. The therapy was satisfactory for patients and showed a beneficial effect on the patients' quality of life.