The equilibrium approach of Silver(1) and Bell and Ghaly(2), is widely used in the industrial design of condensers because it usually gives acceptable accuracy, though it is acknowledged to be less reliable than the film model approach developed by Colburn et al.(3,4). It fails to describe wet wall de-superheating of superheated vapour mixtures but has been successfully modified by McNaught(5) for this case. This work shows that Silver-Bell also fails to describe the condensation of vapour mixtures forming immiscible condensates with acceptable accuracy. A new modification, similar to that of McNaught, is proposed and shown to give good predictions of experimental data, measured in a shell and tube condenser of industrial scale.