The few, rather scarce, and old data on the vapour pressure and sublimation pressure of radon are re-examined in light of the Wagner equation, which is applied for the first time (as far as we are aware) to the sublimation curve. Numerical coefficients have been established for the representation of both equilibrium curves, and estimates are advanced for the coordinates of the critical point, the triple-point, and the normal boiling temperature of radon. Some important thermodynamic properties, e.g., the enthalpies of vaporisation, sublimation, and fusion are derived, and a (p, T) phase diagram is sketched. (c) 2007 Elsevier Ltd. All rights reserved.