The recent advance in our understanding of the relation of protein structure and function cautions that many proteins, or regions of proteins, exist and function without a well-defined three-dimensional structure. These intrinsically disordered/unstructured proteins (IDP/IUP) are frequent in proteomes and carry out essential functions, but their lack of stable structures hampers efforts of solving structures at high resolution by x-ray crystallography and/or NMR. Thus, filtering such proteins/regions out of high-throughput structural genomics pipelines would be of significant benefit in terms of cost and success rate. This chapter outlines the theoretical background of structural disorder, and provides practical advice on the application of advanced bioinformatic predictors to this end, that is to recognize fully/mostly disordered proteins or regions, which are incompatible with structure determination. An emphasis is also given to a somewhat different approach, in which ordered/disordered regions are explicitly delineated to the end of making constructs amenable for structure determination even when disordered regions are present.