For a substantial number of patients with acute pancreatitis, no recognizable causes can be identified and such cases are called "idiopathic". With the introduction of duodenal bile collection for microscopic examination, it became possible to detect minor constituents of the bile, such as cholesterol and/or calcium bilirrubinate crystals. The mechanism by which crystals produce pancreatitis seems to be related to migration of aggregate crystals through the papilla, inducing papillary trauma or temporary impaction which can cause a biliopancreatic reflux. We now report a series of 45 patients with acute pancreatitis idiopathic, 120 with gallstones and 22 alcoholic. Of the patients with idiopathic pancreatitis whom we studied by biliary drainages, 22 were found to have abnormal drainages (MC+) (20 cholesterol crystals and 2 calcium bilirrubinate), 9 patients had more than 10 crystals per slide. The microcrystals positive (MC+) group had significantly higher values for AST (69.8 +/- 1.7) (mean +/- SEM), ALT (123.3 +/- 28.1), FA (252 +/- 28.1), G-GT (144.6 +/- 26.7) and BT (1.83 +/- 0.37) than the microcrystals negative group: AST (19.6 +/- 2.5), ALT (28.3 +/- 5.8), FA (170.5 +/- 15.1), G-GT (54.3 +/- 10.7) and BT (0.76 +/- 0.09). The more 10 crystals group had higher values (AST: 82.0 +/- 29.1, ALT: 143.1 +/- 43.5, FA: 294.8 +/- 57.2, G-GT: 171.8 +/- 38.4, BT: 2.61 +/- 0.82) than in the microcrystals negative group. We concluded that in the absence of other overt causes, the presence of crystals in bile of patients with pancreatitis justifies etiology. The number is not important.