The degradation of the majority of cellular proteins is mediated by the proteasomes. Ubiquitin -dependent proteasomal protein degradation is executed by a number of enzymes that interact to modify the substrates prior to their engagement with the 26S proteasomes. The 26S proteasome is made of two complexes, the 20S and the 19S. The role of 19S is to unfold the proteins to gain entry into the 20S particle, where the protein is cleaved into short peptides. Thus, some of the functions of the 19S complex are expected to be dispensable for degradation of intrinsically disordered proteins, or IDPs. Indeed, in cell -free systems, at least some of the IDPs are digested by 20S particles in the absence of the 19S. In fact, it appears that susceptibility to the 20S proteasome may represent a hallmark of IDPs. Recent evidence suggests that IDPs are susceptible to degradation in vivo by the 20S proteasome as well. The process is ubiquitin independent and takes place by default. However, the process of default degradation can be regulated by different strategies. The described process of IDP degradation provokes new predictions and explanations in the fi eld of protein regulation and functionality.