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 an unique assignment of the light emission to the defect mechanism. Since the corresponding phenomena are numerous and their details have to be clarified before this technique can be used routinely in a quantitative rather than qualitative approach, fundamental investigations were carried out on the basis of test structures. The applicability of quantitative aspects of emission microscopy in practice, i.e. exemplified by some relevant case studies, has further been discussed in this paper.