Endoplasmic reticulum associated degradation (ERAD) is a mechanism, which recognizes misfolded and unfolded proteins of the ER and retrotranslocates them into the cytoplasm for degradation by the ubiquitin-protesome machinery. Since it was discovered, many researches have conducted to contribute to understanding the mechanism of this conserved pathway. Recently, with the significant progresses in identification of new components revolved in substrate recognition, retrotranslocation and ubiquitylation, as well as the development of new techniques in this area, the specific molecular mechanism of ERAD becomes more clear. The recent progress in the ER stress response and the roles of the components related to ERAD process are summarized with focuses on their molecular mechanisms to provide an overview of this field. Also, the model ERAD substrates and the novel strategies recently developed are included.