Medical treatment options for severe, steroid refractory ulcerative colitis (UC) include infliximab (IFX) or cyclosporine (CSA), but general consensus has been that both agents should not be used together or even successively. We report a case of a 17-year-old male with severe UC refractory to IV steroids with successful sequential salvage therapy guided by serum IFX level. After primary lack of response to IFX, an undetectable serum IFX level and elevated IFX antibodies were followed by immediate transition to IV CSA. This case demonstrates the possibility of therapeutic drug monitoring of IFX levels when calculating the risk/benefit ratio for patients with steroid-refractory UC failing primary salvage therapy.