: The Mayo Score [MS], endoscopic Mayo Score [eMS] and the Ulcerative Colitis Index of Severity [UCEIS] are employed in the assessment of ulcerative colitis [UC] severity. This study compared the aforementioned indices in terms of predictory value for response to remission induction treatment with anti-TNF and anti-integrin biologics. : A total of 38 patients were retrospectively evaluated in the study, 23 male and 15 female, aged 18-74 years old who had undergone a total of 53 biological therapy courses with either infliximab [IFX] or vedolizumab [VDZ] at the Department of Gastroenterology of the Medical University of Łódź. The clinical and endoscopic activity of UC was assessed at the outset of biological therapy and the 14th week remission induction assessment juncture. : The study analyzed 19 IFX and 34 VDZ treatment courses. The response rate of patients receiving IFX reached 73.67% and the response rate was 58.82% for VDZ. The mean MS, eMS and UCEIS improved among all patient groups: 8.316 ± 1.974 to 4.158 ± 2.218 ( < 0.05), 2.632 ± 0.597 to 1.790 ± 0.713 ( < 0.05) and 4.790 ± 1.745 to 3.000 ± 1.453 ( < 0.05) for IFX, 7.088 ± 2.234 to 3.618 ± 2.412 ( < 0.05), 2.706 ± 0.524 to 1.677 ± 1.065 ( < 0.05) and 4.235 ± 1.350 to 2.735 ± 1.880 ( < 0.05) for VDZ. : The outcome assessment in induction treatment of UC includes clinical data and endoscopic evaluation. Severity of inflammatory lesion activity according to the eMS and UCEIS indices correlates with the overall disease presentation as evaluated with MS. The UCEIS provides an overall better predictor for biological induction treatment when compared with the eMS in both patient groups, particularly in those receiving VDZ. It provides a promising alternative to the eMS and can be employed for both initial disease severity assessment as well as for treatment response monitoring.