Diagnostics of plasmas using spectroscopy have been used for a long time in astrophysics and discharge physics. Specific experimental techniques and a detailed accounting of the role of the plasma environment on the radiation physics must be used to obtain reliable information from spectroscopic data. Relativistic quantum-mechanical calculations of atomic structure and line strengths using the formalism of the spin-orbit-split transition arrays have been successfully applied to the interpretation of the spectra of many ions with Z > 60. This chapter investigates the effects of the plasma environment on the formation of line and continuum spectra. Since most of the emissions from laser-produced plasmas occur in the wavelength range below 500 Å, X-ray spectrographs are the basic tools for hot-plasma spectroscopy. Crystal spectrographs are useful in the range λ<20 Å and grating spectrographs used near grazing incidence are useful in the range 20<λ<500Å. One disadvantage of the flat crystal spectrometer is that its light collection efficiency is limited.