Mucinous cystadenocarcinoma of the pancreas is among the few potentially curable malignancies of this organ; recognition of the differences between this and other pancreatic tumors is thus of paramount importance. A second example of mucinous cystadenocarcinoma of the pancreas diagnosed by fine needle aspiration, performed under ultrasonographic guidance, is presented, emphasizing both the radiographic distinction from other cystic lesions plus cytologic features not previously stressed. In essence, the cytodiagnosis relies less on cell morphology, which is characteristically bland and relatively monomorphic, than on the presence of extracellular mucin, which must be distinguished from amorphous background material and necrotic debris. The possibility of diagnosing benign mucinous and serous cystadenomas by imaging and cytology is addressed.