A central structure in the secretory pathway of the cell comprises an elaborate endomembranous system with the multifunctional endoplasmic reticulum (ER) as a major constituent. Newly synthesized secretory proteins and a variety of resident proteins of the pathway enter the rough endoplasmic reticulum. Subsequently, the proteins may be sorted selectively to different membrane-delimited organelles including the Golgi apparatus, endosomes, lysosomes and secretory vesicles. Abcam provides antibodies to a new family of ER-associated proteins, the reticulons, which show a tissue specific distribution.