Pancreatic cancer has a very poor prognosis. Current chemotherapy and radiotherapy regimens are only moderately successful. The tumour suppressor genes p53 and p16(INK4a)encode cell cycle regulatory proteins that are important candidates for gene replacement therapy. Over 80% of pancreatic adenocarcinoma cases lack detectable p16 protein while over 60% contain mutated p53 protein. We used replication-deficient recombinant adenoviruses to reintroduce wild-type p16 and p53 into pancreatic cancer cells in vitro and into subcutaneous pancreatic tumours in an animal model to determine the effect on tumour growth. Significant growth inhibition was observed in all five human pancreatic cell lines with these viruses (P < 0.002) compared with similar control viruses expressing either luciferase or beta-galactosidase. G1 arrest was observed in all cell lines 72 h after infection with Adp16. Infection with Adp53 caused significant levels of apoptosis (P < 0.004). Apoptosis was also observed to a lesser degree (P < 0.03) with the Adp16 vector. Subcutaneous pancreatic tumours, generated in nu-nu mice demonstrated significant growth suppression following injection of Adp53, Adp16 and a combination of both Adp53 and Adp16 (P < 0.0001). These results show that transfer of wild-type p53 and p16 produces significant growth suppression of pancreatic cancer in vitro and in vivo.