Transparent and conductive aluminum-doped zinc oxide films have been prepared by RF reactive magnetron sputtering with different substrate temperatures. The structural characteristics of the films were investigated by the X-ray diffractometry, scanning electron microscopy, atomic force microscopy and transmission electron microscopy, while the electric and optical properties of the films were studied by the Hall measurement and optical spectroscopy, respectively. It has been found that all of the films deposited were flat and smooth with a c-axis preferred orientation perpendicular to the substrate. The lowest resistivity obtained in this study was 4.16 x 10(-4) Omega cm for the films deposited at the substrate temperature of 250 degreesC. By calculating the mean free path of electrons, ion impurity scattering is considered to be the dominant factor for the decrease of conductivity. Optical transmittance measurement results show a good transparency within the visible wavelength range for the films deposited at substrate temperatures above 200 degreesC.