Emission microscopy has now become established as an effective technique in terms of reliability physics of industrial semiconductors. This convenient method allows chip verification and failure analysis to be carried out in many applications. Besides this, emission microscopy provides a technique for use in device engineering and the optimization of test structures. The key to using this technique to permit a more sophisticated quantitative analysis lies in a unique assignment of the light emission to the defect mechanism. Since the corresponding phenomena are numerous and their details are not fully clarified in all cases, further investigation is still required before this technique can be used routinely in a quantitative rather than qualitative approach. Some quantitative aspects of emission microscopy with respect to fundamental studies will therefore be outlined in this article, and the applicability of such practical guidelines will be illustrated. This provides the fundamentals for a comprehensive evaluation of the potential applications and degree of informativeness of this advanced method of failure analysis.