Electrospun polymer composite fibers were deposited in the form of aligned arrays onto interdigitated microelectrodes. The fibers consist of an insulating polymer blended with carbon black near the percolation threshold and, therefore, the fiber resistance increases when the polymer component swells during vapor absorption. Microsensors were fabricated from four different cross-selective polymers and the electrical resistance of each element of the four-component sensor array was tested upon exposure to toluene, trichloroethylene, methanol and dichloropentane vapor. The sensitivity and response kinetics of each sensor element was measured for each vapor. The sensor elements exhibited a linear response as a function of vapor concentration and the response time ranged from several seconds to over 1 min. The four organic compounds could be discriminated-based on the unique response pattern from the sensor array. (c) 2005 Elsevier B.V. All rights reserved.