Preliminary evidence suggests that a higher neutrophil-lymphocyte ratio (NLR) may be an indicator of active ulcerative colitis (UC). However, it is not clear whether the NLR is a useful and simple indicator of clinical activity in UC after adjusting for the other inflammatory markers. We designed a retrospective study to evaluate the role of the NLR in estimating disease severity in UC patients. The study consisted of 71 patients with UC and 140 age- and sex-matched healthy individuals (control group). The NLR, erythrocyte sedimentation rate, C-reactive protein, and white blood cell count were measured. The NLR values of the active UC group were elevated compared with those of the patients with inactive UC and the controls (2.59 + 1.47, 2.03 + 1.07, and 1.98 + 0.85, respectively; p = 0.005). The receiver operating characteristic revealed that the optimum NLR cut-off point for active UC was 2.39. A multivariable logistic analysis showed that of the parameters studied, C-reactive protein was the only parameter able to significantly discriminate active from inactive UC (B: 0.222; p = 0.017; odds ratio: 1.248; 95% confidence interval: 1.041-1.497). Copyright (C) 2015, Kaohsiung Medical University. Published by Elsevier Taiwan LLC. All rights reserved.