Polyethylene Glycol (PEG) is a polymer of ethylene oxide available in size variants from 400 Da to 40 kDa. It is nonionic, nontoxic, biocompatible, strong, hydrophilic and has a large exclusion volume in aqueous solution. PEG has a number of industrial and biomedical applications. The modification of a biopharmaceutical with PEG increases its hydrodynamic radius, reduces immunogenicity and proteolytic cleavage. In particular, therapeutic proteins are conjμgated with PEG to slow down their clearance from circulation and improve bioavailability. PEG antibodies can be a vital tool for propelling therapeutics to market by serving as a positive control anti-drμg antibody, measuring clearance of a drμg, or simply as a QA release confirming PEGylation.