Formation of tubular structures from an epithelial tissue is a process common to many morphogenetic events during organogenesis. We report here new data concerning the expression pattern of the vHNF1/HNF1β gene during this process in the mouse. vHNF1 (variant Hepatocyte Nuclear Factor 1) is a member of the HNF1 homeoprotein family. Its expression domain includes organs such as the liver, the kidney, the lung and the pancreas, but is restricted to the epithelial cells of these organs. To follow vHNF1 expression during organogenesis, we have introduced a NLS-lacZ gene under the control of vHNF1 regulatory regions by homologous recombination. Detection of the β-galactosidase activity in heterozygous mice demonstrates that this gene is expressed in numerous tubular epitheliums as soon as they appear and all along development.