WO3 nanofibers with a porous morphology were successfully prepared through electrospinning method with subsequent calcination. The morphology and structure were investigated via X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, and selected area electron diffraction. The results showed that the porous WO3 nanofibers were composed of small grains with the diameter of around 12 nm, which was affected to a large extent by the calcination temperature. Gas sensing investigations revealed that the WO3 nanofiber sensor exhibited excellent response and selectivity to acetone at 270 degrees C with fast response and recovery times, which might substantially benefit from their unique porous structure and large surface area. In addition, the developed sensor presented a detection limit down to 0.1 ppm acetone with good sensing performance even at 95% relative humidity, rendering its potential application in practice, especially in the noninvasive diagnosis of diabetes. The formation mechanism and the acetone sensing mechanism of the porous WO3 nanofiber structure were also discussed. (C) 2015 Elsevier Ltd. All rights reserved.