The results of calculations of the ionisation equilibria and radiative cooling of Tokamak impurities are given as a function of electron temperature. In the relevant rate coefficients, the Maxwellian distribution of electron energies has been assumed to be distorted by a runaway tail caused by the finite electric field in a Tokamak. In order to investigate the effect of runaways on the start-up phase of a Tokamak, non-steady-state calculations have also been performed.