This report describes a newly observed cystic lesion of the pancreas showing acinar cell differentiation. The patients affected by this lesion included seven women and three men (age range 16-66 years). In six patients, all of whom were female and all but one of whom suffered from abdominal pain, the cystic lesions (diameters, 4-15 cm) were detected by imaging techniques and subsequently removed. In four patients the cystic lesions were incidental findings. Eight lesions occurred as unifocal, unilocular or multilocular cysts in the head (n = 6) or tail (n = 2) of the pancreas. One lesion was bifocal (head and tail) and another involved the entire pancreas. The cysts were only rarely connected with the pancreatic duct system, but with acinar structures. Their lining cells expressed pancreatic enzymes and lacked any cellular atypia or proliferative activity (Ki67 index <1%). For a follow-up period of 6-84 months all patients remained alive and well. Although a nonneoplastic nature cannot be fully excluded, we propose that this lesion, composed of well-differentiated acinar cells, may represent the benign counterpart of the well-recognized acinar cystadenocarcinoma. We therefore suggest the term acinar cell cystadenoma.