3,5-Dinitrosalicylic acid (DNS) reagent is widely used in the estimation of reducing sugars. The reagent shows a differential behaviour towards mono- and di-saccharides. This phenomenon has been misinterpreted in the literature. Contrary to the facts, it has been reported that the DNS test is less sensitive for the estimation of cellobiose than it is for the estimation of glucose. This communication clarifies the concept. In addition, the study also compares the reaction of different mono- and di-saccharides and discusses the difference in their reactivity. (C) 2011 Elsevier Ltd. All rights reserved.