The integrity of the main pancreatic duct (MPD) was evaluated by endoscopic retrograde pancreatography (ERP) in a retrospective study of 105 patients with acute pancreatitis presenting over an 11-year period (1980-1991). The findings were compared with clinical outcome and the need to operate for local pancreatic complications. Patients were divided into two groups. Group 1 (n = 89) had either clinically mild pancreatitis or severe disease but no surgery for local complications, and < 25 per cent necrosis on contrast-enhanced computed tomography (CT) (n = 48). Group 2 patients (n = 16) had clinically severe pancreatitis and underwent surgery for local complications and/or had > or = 25 per cent necrosis on CT (n = 12), at surgery or post mortem. All 89 patients in group 1 had an intact MPD at ERP, which was performed a median of 6 (range 0-30) days after onset of pancreatitis; the median age was 63 (range 20-88) years and there were no deaths. The median age of patients in group 2 was 59 (range 26-85) years. ERP in this group was performed in four patients < 5 days after onset and all had an intact MPD; one died with necrosis and another from a cerebrovascular accident. ERP was performed > or = 5 days after onset in the other 12 patients; five had an intact MPD and two required surgery for pseudocyst drainage only; seven had a disrupted MPD and all required surgery for pancreatic necrosis (one death). It is concluded that an intact MPD was a feature of mild pancreatitis, whereas disruption occurred > 4 days after onset in patients with necrosis necessitating surgery.