Two antimony (Sb)-doped tin oxide (ATO) targets of different densities were used to illustrate the chemical evolution of target surfaces during RF magnetron sputtering. The phase compositions, the microstructures, the chemical states, and the electrical and optical properties of the deposited ATO films were revealed. The ATO film deposited by the high-density (98%) target yielded an enhanced electrical conductivity of 3.21 x 10(-2) Omega.cm (under a low power density of 100 W without substrate heating) and excellent optical properties with an average transmittance of 94.65%. For the target with pores and dielectric inclusions, the decrease in Sb content and the variation in the chemical state of tin (Sn) degraded the electrical conductivity and the optical properties of the deposited ATO films. The chemical state of the low-density ATO target varied significantly due to micro-arcing caused by warps in the electrical field during sputtering.