The human organic anion transporters 1 and 3 (OAT1, OAT3) are crucial for the excretion of organic anions in renal proximal tubular cells. Little is known about their transcriptional regulation of expression. For OAT3 a regulation via a cAMP response element (CRE) has been shown by others. The aim of this study is to identify the CREs which are essential for the transcriptional regulation of OAT1. In silico analysis of the OAT1-promoter (-3049/+88) for identification of potential CREs were carried out. A series of reporter constructs were generated by cloning different promoter regions into the pGL3-enhancer. Luciferase assays were performed by transfection of opossum kidney- (OK) cells with reporter constructs and Renilla reniformis vector. For activation of the OAT-promoter, OK-cells were treated 12–16 h with forskolin and with 3-isobutyl-1-methylxanthine (IBMX) before luciferase assay. The in silico analysis revealed nine putative CREs in the OAT1-promoter. All five cloned OAT1 constructs showed promoter activity. To verify our OK-cell system, we used the published OAT3 (-214/+21) promoter and could detect a significant 5-fold induction of the OAT3 after a 12 h incubation with forskolin. Moreover we could show that by using IBMX the endogenous cAMP is sufficient to induce a comparable fold induction of the OAT3 as forskolin does. While using the OAT1 (-342/+88) and OAT1 (-3049/+88) constructs, we found that the first CRE at position -33 to -13 out of nine is essential for cAMP responsive induction of OAT1 expression. In conclusion, PKA activator cAMP is involved in transcriptional regulation of OAT1.