In order for extreme ultraviolet (EUV) plasma sources to become the next generation lithographic source, significant obstacles still need to be overcome. Improvements in conversion efficiency (CE), plasma stability, and component lifetimes are required. Although the final goal is to produce a suitable 13.5 nm light source, solving the full range of issues will require a more thorough understanding the the plasma than just the EUV optical emissions. Because of the complex nature and extreme conditions produced in the EUV plasma sources, many different plasma diagnostics are needed to fully characterize these extreme ultraviolet lithography (EUVL) sources.Although the development of EUV lithography light sources is a relatively recent endeavor, similar plasmas have been utilized for many years for other applications. Laser pulsed plasmas (LPPs) have been used for applications ranging from laser drilling to X-ray lasers. Dense Plasma Pinches (DPPs) have been investigated as potential nuclear fusion sources and also as X-ray sources. Consequently, suitable plasma diagnostics have been developed over many years for the study of these types of plasma sources.This chapter will be concentrating on plasma diagnostics not based on standard optical emission measurements. It will discuss diagnostics for measurements of emitted plasma debris and other basic plasma properties such as electron density and temperature. It includes discussions on surface accumulators, plasma imaging systems (including interferometry), and electron, ion and neutral atom diagnostics.