The cold start transient characteristics of a small methanol reformer for a fuel cell were investigated. The main parameters studied were the oxygen to methanol mol ratio (O/C), fuel supply rate, heating power and heating temperature. The composition of the gas produced by the reformer was analysed. The main aim of this paper was to determine a favorable combination of the parameters for obtaining rapid hydrogen production during the transient behaviour of the reformer. A small methanol reformer with fuel, air and water injectors, heaters and a catalyst was constructed. Vaporised methanol was injected into the reformer, which then flowed into the catalyst. For the purpose of enhancing the response of the cold start transient reaction, eight glow plugs were mounted at the inlet of the catalyst to control the flow temperature together with the adjustment of the oxygen to methanol mol ratio. The best response from cold start was obtained with 960 W heating power. 80degreesC heating temperature. 14 mL/min methanol and 70 L/min air supply rates among the experimented parameters. Under this operation setting, hydrogen was produced after 220 s from cold start with the production rate stabilising after 4-5 min and eventually reaching the highest concentration at 350degreesC. Generally.. hydrogen commenced production at catalyst outlet temperature of 100degreesC and stabilised at 350degreesC. (C) 2004 Elsevier Ltd. All rights reserved.