We generated pdx1^PBCreER™ transgenic mice in which a pancreatic endocrine‐specific enhancer (pdx1^PB) drives expression of a tamoxifen (TM)‐inducible Cre recombinase/estrogen receptor fusion protein. We previously showed that this enhancer directs expression to immature endocrine cells as well as postnatal islets. This transgene provides spatial and temporal control of gene inactivation in pancreatic islets. Three transgenic lines were generated and crossed with R26R mice to assess recombination efficiency. TM‐dependent lacZ expression was observed in islets from all three lines. One line was chosen for further study based on its strong islet‐specific recombination in embryos and adults. In this line, a dose‐dependent increase in recombination efficiency was observed in endocrine cells. Our data suggest that this transgenic line will be a valuable tool to inactivate genes in pancreatic endocrine cells during development or in the adult. The dose‐dependent nature of recombination suggests a potential use for this line in the generation of genetic mosaic animals. genesis 42:210–217, 2005. © 2005 Wiley‐Liss, Inc.