A new anhydrous high-pressure synthesis route was developed for rutile type RhO2. Rhodium(III) chloride was reacted with Na2O2 at 600 °C under an oxygen pressure of 200 MPa yielding RhO2 and NaCl. X-ray powder diffractometer data and TEM observations confirmed the rutile structure: P42/mnm, a = 448.7(1), c = 308.9(1) pm, x(O) = 0.3125(8), leading to Rh-O distances of 195.0 (4x) and 198.3 pm (2x) in the slightly elongated octahedra. Structural transformations associated with the production of oxygen vacancies can be initiated by electron-beam heating.