PTHrP mRNA was quantified by RT-PCR and the localization of PTHrP mRNA was determined by in situ hybridization in kidney. During development, the expression of PTHrP mRNA is much higher before 2 weeks of age while kidney is developing. In E16 fetal mice, PTHrP mRNA was strongly expressed in the collecting ducts, urothelium of the pelvis, tubles, the glomeruli and immature elements in the cortex of the developing kidney (nephrogenic zone). within 0-day-old-mice, it was dominantly expressed in collecting ducts, the urothelium of the pelvis and nephrogenic zone. These findings suggest that PTHrP plays a role in kidney development as an autocrine/ paracrine factor.