Abstract The crystal structure of Tl 0.5Bi 0.5Sr 2CuO 5 was determined by powder x-ray diffraction with the Rietveld method. The structure of Tl 0.5Bi 0.5Sr 2CuO 5 is analogous to TlSr 2CuO 5, having a tetragonal structure with space group P4 mmm and a=3.7527(1) A ̊ and c=9.0278(4) A ̊ . Similarities and differences between Tl 0.5Bi 0.5Sr 2CuO 5 and other Tl-based cuprate materials are discussed. Structural and physical properties of solid solutions of Tl 1−xBi xSr 2CuO 5 (0.20≤x≤0.50) were also studied as a function of Bi stoichiometry. Superconductivity was not found in any of the compositions; all of the samples show only metal-like properties.