This review examines the appropriate timing of intervention in acute pancreatitis. In gallstone pancreatitis, it is now clear that cholecystectomy during the primary admission carries no greater risk of complications than delayed cholecystectomy and enables earlier recovery to normal activity. This course of action pre-empts a second, possibly fatal attack of acute pancreatitis. Cholecystectomy should be done after the acute phase has settled, before discharge from hospital. Patients with gallstones should now be offered endoscopic sphincterotomy within 48 hours of admission. This approach is safe, and reduces the risk of complications. When complications develop, early necrosectomy is only indicated if conservative measures fail. Delayed (> 10 days) necrosectomy is appropriate if there is evidence of sepsis, or clinical failure to improve. Pancreatic pseudocysts can often be managed expectantly; a high proportion will resolve spontaneously. After a delay of 12 weeks, persistent cysts require evaluation by endoscopic pancreatography, which gives crucial information in the choice between percutaneous or surgical drainage of the pseudocyst. A patient with pancreatitis is usually treated under the care of a surgeon, who has traditionally taken the decision on the timing of any intervention, and has performed such intervention at open operation. Recently, the development of alternative techniques has enabled the surgeon to call on the skills of his colleagues in endoscopy and interventional radiology. However, the availability of these alternatives to surgery should not affect the timing of intervention unless it can be clearly shown that such a change in timing combined with the minimally invasive technique can improve the outcome for the patient. Intervention may be required to deal with gallstones in the gallbladder or in the bile duct, to deal with, or ideally prevent, the deleterious systemic effects of pancreatic and peripancreatic necrosis, or to drain a peripancreatic abscess. Peripancreatic fluid collections and pancreatic pseudocysts may also require either internal or external drainage to relieve symptoms or prevent complications.