Abstract: The need for back-streaming ion diagnostics is addressed, and various experimental methods for its implementation are reviewed. With regard to the main parameters that must be measured (density, velocity, type, and so on), the basic principles, characteristics and limitations of specific methods based on laser interferometry, Faraday cups, Langmuir probes and solid track detectors are analyzed in detail. Their design and the calculation of possible experimental results are described, with particular emphasis on the measurement of back-streaming ions using Langmuir probes. Based on information fusion technology and analysis of the above-mentioned methods, an integrated diagnostic scheme is proposed, and an estimate given of the results that may be expected.