In Stat3lox/lox mice that express Cre recombinase under the control of the Pdx1 promoter,12, 13 some studies excluded a role for STAT3 in the development and function of the pancreatic β-cells,13 whereas others observed glucose intolerance and impaired insulin secretion as a result of reduced VEGF-A signaling and abnormal islet vascularization.12, 14Stat3lox/lox mice with insulin promotor-driven Cre recombinase are glucose intolerant.15, 16 Although these studies suggest a contribution for STAT3 in β-cell function,16 its role in β-cell proliferation and survival is unknown. This evidence concerns the gene INS and Glucose intolerance.