Abstract.  The Plasma Focus is a device with wide-ranging application potential due to its intense radiation of SXR, XR, electron and ion beams and fusion neutrons when operated in Deuterium. We discuss here the modelling using the 5-phase Lee Model code of the focus when operated in various gases generally and using examples drawn from D, D-T, He, Ne, N, O, Ar, Kr and Xe. For D, D-T and He a fully ionized model is used throughout the five phases. For the heavier gases from Ne onwards a corona model is used to generate the thermodynamic data required in the computation. The use of gases such as Ne and Xe for generation of specific SXR or EUV lines for micro-lithography applications has now been widely discussed in the literature as have the use of N and O to generate the lines suitable for water-window microscopy. Recently Ar has been considered for micro-machining due to the harder characteristic line radiation. Various gases including Kr have been discussed and used for fusion neutron yield enhancement due arguably to mechanisms such as thermodynamically enhanced pinch compressions. In this paper we also look at the effect of radiation cooling and radiation collapse in the heavier noble gases. The Pease-Braginskii current is known to be that current flowing in a hydrogen pinch which is just large enough for the Bremsstrahlung to balance Joule heating. This radiation-cooled threshold current for a hydrogen pinch is 1.6MA, the ‘Pease-Braginskii current’. It is known that in gases undergoing line radiation strongly the radiation-cooled threshold current is considerably lowered. We show that the equations of the Lee Model code may be used to compute this lowering. The code also shows the effect of radiation cooling when operated in the relevant regimes. It is suggested that the neutron enhancement effect of seeding could at least in part be due to the enhanced compression caused by radiation cooling.