The magnetic field dependence of the transmission of 24 GHz radiation through ferromagnetic plates of Supermalloy approximately 10−2 cm thick has been investigated. The results have been interpreted using a theory which combines Maxwell's equations and the equation of motion for the magnetization, and which includes the possibility of the external magnetic field lying at any angle with respect to the specimen normal. The results of the measurements on four discs of Supermalloy at 1 °C were very consistent and resulted in the average values g = 2.106 ± 0.001, 4π7Ms = 7.531 ± 0.01 kOe, and a damping parameter, λ = (0.94 ± 0.05) × 108 s−1. Although transmission studies made on specimens thick compared to the skin depth are very useful for obtaining the magnetic damping parameter and magnetostatic parameters, the article also discusses the possibility of using transmission experiments on thinner specimens to study exchange and surface pinning of the magnetization.