[en] The use of the ultrashort-lived radionuclide Ir-191m (T₁2/=5s) for first-pass radionuclide angiography produces lower patient radiation dose, higher photon flux, and allows repeated studies that are not possible with the radionuclide currently employed for these studies (Tc-99m; T₁2/=6h). An Os-191->Ir-191m radionuclide generator suitable for human use was developed in our laboratory and has been used in a number of clinical studies. This generator design suffers, however, from high breakthrough (5 x 10^-₃%), low yield (10-15%), and an eluent (pH 1 saline) that must be buffered prior to injection. In an effort to increase Ir-191m yield and decrease Os-191 breakthrough, the generator assembly process has been examined carefully and a detailed, reproducible assembly process developed. A variety of approaches have been used in an attempt to improve the performance of the current generator design but, as yet, only modest improvements have been realized. The investigation of new generator designs has, however, produced a new generator with substantially higher yield (30-35%), lower breakthrough (2-3 x 10^-₃%), and an eluent that does not require buffering prior to injection. Efforts are currently underway to improve the stability and evaluate the toxicity of this system