Various metal oxide nanowires, such as ZnO, SnO2, Fe2O3, In2O3 and Ga2O3, have been synthesized by chemical vapor deposition method. Their structures and properties are characterized by TEM, SEM, XRD, AFM, photoluminescence, photoconductance, scanning surface potential microscopy, and electrical transport measurement. By integrating bottom-up technique with top-down lithographic technique, these nanostructures are used to fabricate a range of electronic and chemical sensing devices. As an example, individual ZnO nanowires are configured as n-channel field effect transistors, and implemented as highly sensitive chemical sensors for detection of NO2, NH3, CO toxic gases. Due to a Debye screening length comparable to the nanowire diameter, the electric field applied over the back gate electrode is found to significantly affect the sensitivity. Applying a strong negative field at the gate electrode is able to efficiently refresh the sensors by an electro-desorption mechanism. Furthermore, different chemisorbed species could be distinguished from the "refresh" threshold voltage and the temporal response of the conductance. These results demonstrate a refreshable field effect sensor with a potential gas identification function. Other material systems and current state-of-the-art research will also be presented. As a whole, the study of the metal oxide nanowires paves the way to the future development of nanoscale electronic, optoelectronic and chemical sensing devices.