Oscillations in a B-Z system with oxalic acid (OA) + xylose (XY) as mixed organic substrates have been investigated. Neither of them acts as bromine scavenger and oscillations do not occur when either of them is used as organic substrate. Studies have been made for varying concentrations of OA but keeping XY fixed. Both single and dual frequency oscillations are observed. [Br-2] and [Br-] during oscillations were measured spectrophotometrically and electrochemically, respectively. Oscillations are quenched by addition of higher [Br-] in the case of both type II oscillations and I. Experimental results support the mechanism for B-Z oscillations involving use of OA and fructose (F) and OA and glucose (G) as mixed substrates. (C) 2004 Elsevier B.V. All rights reserved.