The gas-phase rate coefficient for the reaction of thiophene with nitrate radical. NO3, has been determined, using relative (gas chromatography as analytical tool) and absolute methods at 298 K. The absolute experiments were carried out using a fast-flow-discharge technique, with detection of the NO, radical by Laser Induced Fluorescence (LIF). The proposed rate coefficient at 298 K is. k = (3.16 +/- 0.27) x 10(-14) cm(3) molecule(-1) s(-1). The temperature dependence was studied by the absolute technique in the range 260-433 K. observing that in the interval of 260-277 K the rate coefficient decreases as the temperature increases and from 298 K onwards the rate coefficient increases with temperature. (C) 2002 Elsevier Science B.V. All rights reserved.