Continuous diamond films have been grown on mirror-polished silicon, polycrystalline copper, SiC and high oriented pyrolytic graphite substrates using hot filament assisted chemical vapor deposition. Instead of using conventional gaseous carbon source, a graphite plate was used as the carbon source with hydrogen as the only feeding gas. No substrate pretreatment such as diamond powder scratching or negative biasing was needed. When carbon-13 was used as the carbon source, only diamond-12. was detected on carbon-13 indicating that deposition rather than direct conversion of carbon to diamond occurred. High nucleation density and conversion efficiency were obtained for the present growing process. Diamond films grown by this method were found to be particularly pure in diamond content.