Preparation of superconducting Tl-Ba-Ca-Cu-O thin films by diffusion of Tl into laser evaporated Ba2Ca2Cu3Ox thin films is reported. From a sintered Ba2Ca2Cu3Ox bulk sample we prepared using a pulsed Nd:YAG laser, Ba-Ca-Cu-O thin films on sapphire and SrTiO3 single-crystal substrates. Subsequently the films were loaded with Tl by simultaneously annealing the films together with a sintered Tl2Ba2Ca2Cu3O10 sample both enclosed in a small stainless steel box; in our procedure Tl contamination was reduced to a minimum. Tc values near 100 K and critical currents of 5·103 A/cm2 at 77 K were obtained.