BACKGROUND: The kidney develops from an intimate interaction between the ureteric bud and the metanephric mass. We attempted to differentially stain the derivatives of the ureteric bud and the metanephric mass in ovine fetuses. METHODS: After appropriate approval, 47 fetal lambs' kidneys at 50 (4), 60 (6), 70 (5), 80 (4), 100 (10), 110 (8), 145 (10) days' gestation (term is 140-145 days) were obtained. After confirming the pregnancy, the sheep were anesthetized, and the fetuses sacrificed. The fetal kidneys were prepared for histological examination, using immunostaining for β-catenin, Laminin, CK34βE12, CK7, E-cadherin, and EMA. RESULTS: In the nephrogenic zone, positive staining was only seen for β-catenin and Laminin. Areas with linear β-catenin expression increased with increasing gestational age, whereas cytoplasmic granular expression in the nephrogenic zone diminished. At 50 days, Laminin-positive cells appeared in the ureteric bud epithelial cells, but not in the proximal tubule epithelium. They were found only in the immature collecting duct at 60 days. CONCLUSION: We have shown that the distribution of β-catenin and Laminin positive-stained cells initially appearing in the ureteric bud changes with gestational age. Further studies may help inform the optimal timing of fetal shunt insertion in obstructive uropathy.