Cytologic patterns in juice from human pancreatic transplants: correlation with histologic findings in the graft. In 19 patients who had undergone pancreatic transplantation with temporary exteriorization of the pancreatic juice, graft tissue became available for histologic examination. In these patients the cytologic patterns in the pancreatic juice were compared with the histologic findings in the graft specimens. In five samples the diagnosis by cytologic studies was rejection. Acute rejection was confirmed in all the histologic specimens. In eight cytologic samples, graft pancreatitis was suspected because of the increased amounts of neutrophils, degenerating cells, epithelial cells, monocytes, and some macrophages, with or without necrotic tissue fragments. All eight histologic specimens showed findings characteristic of pancreatitis. In three cytologic samples, bacteria or fungi were observed. Histologic examination of these patients showed graft pancreatitis. In four patients the cytologic findings were normal. Graft histologic factors were normal in two instances. In one of these grafts there was graft pancreatitis, and in one graft chronic vascular rejection was seen. Our study shows that two different pathologic events occurring in the pancreatic graft (i.e., acute rejection and pancreatitis) are reflected by characteristic changes in pancreatic juice cytology. 