Introduction: Thiopurine (TP) medications i.e. Azathioprine (AZA) and 6-Mercaptopurine (6-MP), are integral components in the management of ulcerative colitis (UC). However, there is limited data on long term effectiveness of TP among UC patients. Our aim was to determine steroid free remission after starting TP in a nationwide cohort of UC patients. Methods: We conducted a retrospective cohort study using the Veterans Affairs (VA) database, which is the largest integrated healthcare system in the United States. We used an internally validated algorithm to identify patients with UC. The cohort study period was from January 1, 2000 to June 30, 2016. The follow-up (FU) began at the date of first thiopurine prescription in the VA pharmacy records and ended if the patient died, had a UC related colectomy or last recorded date in the VAHS if it was not the end of study period. Our outcome of interest was steroid free clinical remission. Results: Our cohort included a total of 5931 UC patients who had utilized thiopurines for management of their disease. The majority of these patients were males (93.86%) and Caucasians (85.25%). A total of 3771 patients (63.58%) had received AZA for their UC and the remaining were on 6-MP. (Table 1) We found that almost 71% of patients continued TP beyond 6 months. At the end of 4 years of the original cohort 36% were still on the drug. Of the patients who continued TP beyond 4 years, almost a third required oral prednisone at some point in their follow up and 4.2 % used IV prednisone. (Table 2) Conclusion: The largest drop off of TP usage occurs in the first 6 months. Almost a third of the patients continued the drug beyond 4 years and of those, the majority remained in steroid free remission.665_A Figure 1. Demographics of our cohort665_B Figure 2. Comparison between thiopurine and steroid usage