Superconducting Pb- and Bi-doped TlBaCaCuO films can be prepared on a variety of substrates by a two-step process, based on metal-organic chemical vapor deposition (MOCVD). MBaCaCuO films (M Pb or Bi) are first prepared by MOCVD using precursors exhibiting improved thermal stability and volatility over previously used complexes. These characteristics allow better control over the stoichiometry of the deposited films. In the second step, thallium is incorporated into these films by a vapor diffusion process using mixtures of Tl 2O 3, BaO, CaO and CuO of specific composition as the source of volatile thallium oxides. The resultant films consist predominantly of single-phase TlMBaCaCuO exhibiting preferential orientation of the CuO planes parallel to the substrate surface. The superconducting properties of these films have been examined by resistivity and magnetization measurements.