<i>Background:</i> Autosomal dominant polycystic kidney disease (ADPKD) is a common human genetic disease that is caused by a mutation of a single gene inherited from either parent. Mutations in the Pkd1 gene result in the formation of multiple fluid-filled cysts in kidneys. In previous studies, the functional regulatory sequences of Pkd1 promoter region were detected by the use of comparative genome analysis. <i>Methods:</i> To investigate the transcriptional regulation of the Pkd1 gene, the Pkd1 promoter was isolated. This promoter contains three Sp1-binding sites. Two of the sites which are found in a 300 bp fragment (–127 to +157) were mutated. An electrophoretic mobility shift assay (EMSA) was performed to determine which transcription factors are bound to Pkd1. <i>Results:</i> Based on studies using a luciferase assay, the Sp1-A site (the nearest Sp1 to the ATG start codon) is more important for activation of Pkd1. The result of EMSA showed that Sp1 transcription factor binds with Pkd1 promoter regions. <i>Conclusions:</i> Two of the Sp1 sites were found in a proximal promoter region of Pkd1 (–127 to +157). Sp1 sites affect an important role in the activation of the gene. Especially, the Sp1-A site is more important for expression of Pkd1.