Ti1-xVxO2 oxides were produced by a coprecipitation process using TiCl4 and VOCl3 as starting materials. As-precipitated gels were calcined at 500~800°C, either in a vacuum or oxygen atmosphere. Effects of the calcination atmosphere and temperature on the phase transition of crystalline Ti-V-O oxides were studied. Calcination in an oxygen atmosphere produced Ti-V-O oxides, which are mixtures of TiO2 and V2O5 oxides formed for all the calcination temperatures. Calcinations at 800°C in vacuum resulted in the formation of a rutile Ti1-xVxO2 single phase for all compositions of vanadium. A significant portion of vanadium ions is incorporated into the TiO2 lattice, which consistently decreases the lattice parameters of the rutile Ti1-xVxO2 phase as the vanadium addition increases.