Ulcerative colitis is a chronic inflammatory disease that always affects the rectum (proctitis), and from there the inflammation can spread proximally, causing inflammation of the entire colon (pancolitis). In the treatment of ulcerative colitis, 5-aminosalicylates, corticosteroids, immunosuppressants biological therapy and janus kinase inhibitors and sphingozine receptor-1 modulators are used. In this research, we collected data on patients diagnosed with ulcerative colitis who were treated with vedolizumab in the Day Hospital of the Department of Gastroenterology and hepatology of the Clinic for Internal Diseases KBC Zagreb in the period from 1/1/2017 until 1/1/ 2022 and evaluated whether the effectiveness of vedolizumab in achieving mucosal healing and histological remission is greater when it is used as the first line of therapy. A total of 66 patients were included, of which 18 (27.3%) received vedolizumab as the first line of therapy. Mucosal healing was achieved in 32 patients (53,3%), and 11 of them (34,4%) received vedolizumab as the first line of therapy (OR 1,87 , p=0,264). Histological remission of the disease was achieved in 19 (33,9%) patients, and of those 19 patients, 7 of them received vedolizumab as the first line of therapy (36,8%, OR 1,58, p=0,543) . In conclusion, from our results, there is no statistically significant association between the use of vedolizumab as the first line treatment and greater efficacy in achieving mucosal healing and histological remission.