A low-noise electronic system is built and tested for fluctuation enhanced sensing. This latter is a new technique and based on the determination of the power spectral density of the stationary resistance fluctuations of semiconductor gas sensors. Its use is advantageous for improving the chemical selectivity of sensors. However, subsequent to an initial fast change of the sensor mean resistance, as a sensor is exposed to an analyte gas, a typical drift of the resistance can be observed. This effect hinders evolving stacionary conditions and thus acquiring fast measurements when applying fluctuation enhanced sensing. Therefore, this drift effect is studied both experimentally and theoretically. Functionalized carbon nanotube layers on silicon chips serve as active material for the experimental investigations. Power spectral density functions are measured and simulated numerically with and without drift conditions. The results are compared and the effect of resistive drift on fluctuation enhanced sensing is discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)