© 2014 BJS Society Ltd. Results: Forty-seven patients were treated in the first interval and 53 in the second. There was no difference in patient demographics, clinical or walled-off necrosis characteristics and laboratory parameters between the groups, apart from a higher proportion of women and Caucasians in the later period. The treatment success rate was higher for the algorithmic approach compared with conventional treatment (91 versus 60 per cent respectively; P <0·001). On multivariable logistic regression, management based on the algorithm was the only predictor of treatment success (odds ratio 6·51, 95 per cent c.i. 2·19 to 19·37; P = 0·001).Conclusion: An algorithmic approach to pancreatic and peripancreatic walled-off necrosis, based on the collection size, location and stepwise response to intervention, resulted in an improved rate of treatment success compared with conventional endoscopic management.Background: The aim of the study was to compare the outcomes of patients with pancreatic or peripancreatic walled-off necrosis by endoscopy using the conventional approach versus an algorithmic approach based on the collection size, location and stepwise response to intervention.Methods: This was an observational before-after study of consecutive patients managed over two time intervals. In the initial period (2004-2009) symptomatic patients with walled-off necrosis underwent conventional single transmural drainage with placement of two stents and a nasocystic catheter, followed by direct endoscopic necrosectomy, if required. In the later period (2010-2013) an algorithmic approach was adopted based on size and extent of the walled-off necrosis and stepwise response to intervention. The main outcome was treatment success, defined as a reduction in walled-off necrosis size to 2 cm or less on CT after 8 weeks.