AbstractHere, we examine the role of GDF11 in pancreatic development. Using in situ hybridization and reverse transcriptase‐polymerase chain reaction analyses, we show that Gdf11 transcripts are expressed in embryonic pancreas epithelium before the secondary transition but decrease rapidly afterward. To determine the function of GDF11 during pancreas development, we analyzed Gdf11−/− mouse embryos. In such embryos, pancreas size is twofold reduced at embryonic day (E) 18 compared with wild‐type littermates. Quantification of the different tissue compartments shows a specific hypoplasia of the exocrine compartment, while the endocrine and ductal compartments are unaffected. Notably, NGN3+ endocrine precursor cells are increased fourfold at E18, although the amount of endocrine cells in the pancreas of these animals is unchanged compared with wild‐type littermates. Similarly, the maturation of endocrine cells as well as the ratio between α‐ and β‐cells appears normal. Developmental Dynamics 235:3016–3025, 2006. © 2006 Wiley‐Liss, Inc.