Initial results from The JET Collective Thomson Scattering diagnostic are presented along \Vith estimates of its full diagnostic capability. It is shown that for diagnosis of alpha particle distributions electron cyclotron emission (ECE) received via wall reflections must be reduced by installation of a viewing dump and that at the highest temperatures down shifted ECE radiation in direct view of the receiver is a serious limitation. Finally it is shown that significant anisotropies must be expected in the distributions of thermo­nuclear fusion products. Methods of diagnosing such anisotropies are being considered.