BACKGROUND: Corticosteroids are recommended only for induction of remission in inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease (CD). This study aimed to evaluate the change in pharmacologic treatment use, particularly systemic corticosteroids, over approximately 30 years, and the impact of biologics on IBD treatment since their appearance in the 2000s. METHODS: This retrospective study conducted in Japan used data from the Phoenix cohort database (January 1990 to March 2021). Patients with disease onset at age ≥ 10 years who received treatment for UC or CD between January 1990 and March 2021 were included. Outcome measures were change in IBD treatments used, total cumulative corticosteroid doses, initial corticosteroid dose, duration of corticosteroid treatment, and surgery rate. RESULTS: A total of 1066 and 579 patients with UC and CD, respectively, were included. In UC, the rate of corticosteroid use as initial treatment was relatively stable regardless of the year of disease onset; however, in CD, its rate decreased in patients who had disease onset after 2006 (before 2006: 14.3-27.8% vs. after 2006: 6.6-10.5%). Compared with patients with disease onset before biologics became available, cumulative corticosteroid doses in both UC and CD, and the surgery rate in CD only, were lower in those with disease onset after biologics became available. CONCLUSIONS: Since biologics became available, corticosteroid use appears to have decreased, with more appropriate use. Furthermore, use of biologics may reduce surgery rates, particularly in patients with CD. UMIN Clinical Trials Registry; UMIN000035384.