Caspase-3/CPP32, a member of the Ced-3-family of cysteine proteases, is an important mediator of programmed cell death (apoptosis). Intraductal papillary-mucinous tumor of the pancreas (IPMT) is a unique tumor that grows intraductally with rare stromal invasion. However, it is not possible to distinguish noninvasive from invasive IPMT preoperatively. To examine whether caspase-3 expression reflects the biological behavior of pancreatic tumors, we investigated this enzyme expression by reverse transcription-polymerase chain reaction (RT-PCR) and immunohistochemistry in 22 pancreatic duct cell carcinomas (PDC) and 13 IPMT cases. Caspase-3 mRNA was overexpressed in PDC and IPMT with carcinoma when compared with normal pancreatic tissue or IPMT with adenoma. The immunoreactivity of this enzyme was predominantly found in the cytoplasm of invasive tumors (PDC and invasive IPMT). There was a significant correlation between the cytoplasmic staining and malignant grade of the tumors. In contrast, the nuclear expression of this enzyme was significantly higher in noninvasive than in invasive tumors (p = 0.0015). Cytoplasmic expression of caspase-3 may be related to the invasiveness of pancreatic tumors. In contrast, nuclear expression of this enzyme may reflect the benign biological behavior of IPMT.