[en] Laser-plasma interaction experiments have now advanced to the point where very quantitative measurements are required to elucidate the physics issues important for laser fusion and other applications. Detailed time-resolved knowledge of the plasma density, temperature, velocity gradients, spatial structure, heat flow characteristics, radiation emission, etc. are needed over tremendous ranges of plasma density and temperature. Moreover, the time scales are very short, aggrevating the difficulty of the measurments further. Nonetheless, such substantial progress has been made in diagnostic development during the past few years that we are now able to do well diagnosed experiments. In this paper we will review diagnostic developments for laser-plasma interactions, outline their regimes of applicability, and show examples of their utility. In addition to diagnostics for high densities and temperatures characteristics of laser fusion physics studies, diagnostics designed to study the two-stream interactions of laser created plasma flowing through an ambient low density plasma will be described