['Preclinical in vivo research on inflammatory bowel diseases requires proper animal models and techniques allowing longitudinal monitoring of colonic inflammation without the need to kill animals. We evaluated colonoscopy and μ-positron emission tomography/computed tomography (μPET/CT) as monitoring tools in a model for chronic colitis in mice.', 'Colitis was induced by adoptive transfer of CD4(+)CD25(-)CD62L(+) T cells in immunocompromised severe combined immunodeficient mice. Three study protocols were designed. In study 1, colonoscopy and µPET/CT were performed once, 4 weeks after transfer. In study 2 and study 3, colitis was sequentially followed up through colonoscopy (study 2) or colonoscopy plus µPET/CT (study 3). Each study included postmortem evaluation of colonic inflammation (macroscopy, microscopy, and myeloperoxidase activity).', 'In study 1, both colonoscopy and µPET/CT detected colitis 4 weeks after transfer. Study 2 showed a gradual increase in colonoscopic score from week 2 (1.4 ± 0.6) to week 8 (6.0 ± 1.1). In study 3, colitis was detected 2 weeks after transfer by µPET/CT (2.0 ± 0.4) but not by colonoscopy, whereas both techniques detected inflammation 4 and 6 weeks after transfer. Colonoscopy correlated with µPET/CT (r = 0.812, 0.884, and 0.781, respectively) and with postmortem analyses in all 3 studies.'] Are colonoscopy and µPET/CT valid techniques to monitor inflammation in the adoptive transfer colitis model in mice?