Through-focus electron holography and quantitative electron diffraction have been applied to determine the structure of the 21 K superconductor ThPdx B6-2x with x ≈ 0.65. This compound adopts a cubic structure (a = 0.42nm; space group, Pm 3 m), which is an intermediate between the structures of the CaB6 and Cu3Au. Short-range ordering results in a superstructure as is evident from diffuse streaks in the electron diffraction pattern. © 1995 Taylor & Francis Ltd.