Recognition and elimination of misfolded proteins are essential cellular 
processes. More than thirty percent of the cellular proteins are proteins of the 
secretory pathway. They fold in the lumen or membrane of the endoplasmic 
reticulum from where they are sorted to their site of action. The folding 
process, as well as any refolding after cell stress, depends on chaperone 
activity. In case proteins are unable to acquire their native conformation, 
chaperones with different substrate specificity and activity guide them to 
elimination. For most misfolded proteins of the endoplasmic reticulum this 
requires retro-translocation to the cytosol and polyubiquitylation of the 
misfolded protein by an endoplasmic reticulum associated machinery. Thereafter 
ubiquitylated proteins are guided to the proteasome for degradation. This review 
summarizes our up to date knowledge of chaperone classes and chaperone function 
in endoplasmic reticulum associated degradation of protein waste.