The composition and structure of InN films, prepared by reactive r.f. magnetron sputtering method using nitrogen in the range from 0-100% in the nitrogen/argon gas mixture during sputtering, have been investigated. X-ray diffraction and Auger electron spectroscopy results show that the phase of the deposited films change from In, to In + InN and to InN as nitrogen content in the sputtering gas is increased. The InN films with wurtzite structure can be grown in the range of 40-100% nitrogen content in the sputtering gas, however, highly c-axis preferred InN films are obtained only when pure nitrogen is used as the sputtering gas.