The International Study Group for Pancreatic Fistula (ISGPF) made the first attempt to standardize the outcome measure of fistulas in the field of pancreatic surgery by publishing the definition and classification of postoperative pancreatic fistulas (POPFs) in 2005. POPFs were determined by any measurable volume of fluid output via an operatively placed drain with amylase activity greater than three times the upper normal serum value. Taking into account more than 10 years of reported experience worldwide, the updated definition published in 2016 by the reconvened International Study Group for Pancreatic Surgery (ISGPS) attempted to overcome the limits of the previous classification. The crucial concept of POPF clinical significance was introduced by eliminating grade A from the fistula scenario. The wider use of interventional procedures has also made it necessary to recode grade C POPFs, which now have clearer boundaries, toward the worst end of the severity scale. Grade B still represents the most prevalent and heterogeneous category of POPFs, both in terms of clinical burden and management. In the near future, further efforts will be required to better stratify grade B POPFs to standardize treatment strategies and compare outcomes among institutions.