This work focuses on tracking ulcerative colitis in mice. High labeling yield and radiochemical purity were achieved for the formation of a [(125/131) I]balsalazide radiotracer at optimum conditions of oxidizing agent content (chloramines-T [Ch-T], 75 mug), substrate amount (100 mug), pH of reaction mixture (6), reaction time (30 min), and temperature (37 degrees C), using radioactive iodine-125 (200-450 MBq). The radiolabeled compound, [(125/131) I]balsalazide, was stable in serum and saline solution during 24 h. Balsalazide is acting as a peroxisome proliferator-activated receptor (PPARgamma). Biodistribution studies were carried in normal and ulcerated colon mice. High uptake of 75 +/- 1.90% injected dose/g organ (ID/g) observed in ulcerated mice confirmed the suitability of [(131) I]balsalazide as a novel radiotracer for ulcerative colitis imaging in mice.