The mutation of the PKD1 gene causes autosomal dominant polycystic kidney disease (ADPKD), and the PKD1 gene encodes polycystin-1 (PC-1). PC-1 is thought to be a cell-cell/matrix adhesion receptor molecule at the cell surface that is widely expressed in the kidney. However, there are controversies about the role of PC-1 protein and its expression when using different antibodies to detect it. We used two PC-1 antibodies; C-20 (Santa Cruz, sc-10372) as the C-terminal antibody, and P-15 (Santa Cruz, sc-10307) as the N-terminal antibody. We evaluated the PC-1 expression by performing immunoblotting on the human embryonic kidney (HEK) 293 cells and the renal proximal tubular epithelial cell (RPTEC) lysates. We characterized the expression of PC-1 in the fetal, adult and polycystic kidneys tissues by performing immunohistochemistry. We confirmed the PC-1 expression in the HEK 293 cells and the RPTEC lysates, but the expression was very low. The PC-1 proteins were diffusely expressed in the tubular epithelial cells cytoplasm in the fetal and adult kidneys, and the PC-1 expression was more prominent in the proximal tubules of the fetal kidney. In the ADPKD kidney, the PC-1 proteins were heterogenously and weakly expressed in the tubular or cyst lining epithelial cells. Our data suggests that the development of the kidney may regulate the expression of PC-1, and an altered PC-1 expression may contribute to cyst formation in ADPKD.