We present the current status-of-the-art in Stark broadening theory as a theoretical basis for diagnostics of low temperature plasmas in gas discharges, and of high temperature laser produced or z-pinch dense plasmas. The diagnostics abilities vary depending on the parameters of the gas discharges, or on the range of intensity, and duration of the laser or z-pinch pulses. In the case of high temperature plasmas, besides the conventional diagnostics based on the Stark broadening, the contemporary possibilities of UV and XUV interferometry for plasma density measurements and of tomography reconstruction of the macroscopic gradients of temperature and densities in laser produced plasmas are discussed.