Pancreatic morphology and amylase release from isolated pancreatic acini in response to caerulein was studied in the course of an experimental bile induced acute pancreatitis without acinar necrosis. The inflammation was induced by retrograde microinfusion of 25 microliters bile into the rat bile pancreatic duct. A dissociation between functional and structural findings was seen. One hour after the bile injury, there was a transient change in acinar cell function. The response to stimulation by caerulein was reduced by 50%, whereas the sensitivity to caerulein was normal. There was oedema and an initial leucocyte infiltration of the gland. Six hours, one day, three days, and seven days after the bile injury, there was an acute interstitial oedematous pancreatitis with a modest polymorphonuclear leucocyte infiltration of the interstitium and widespread acinar vacuolisation. Morphological changes were most pronounced at the third postoperative day. Acinar amylase release, however, was normal both in terms of sensitivity and responsiveness to stimulation. These results show that bile injury may result in an initial disturbance of acinar cell function. Normal acinar amylase release prevailing in the course of the inflammation suggests that disturbance of the acinar amylase secretory response is not a primary stimulant of the inflammation before the development of acinar necrosis.