As a step toward the elucidation of human Ang II type 1 receptor gene expression, the genomic organization of the human AT1 receptor was investigated. Comparison of the genomic DNA and cDNA sequences revealed that it consists of at least five exons. The length of the AT1 receptor gene is greater than 55 kb, and the size of the exons ranges from 59 to 2,014 base pairs. Four of the exons encoded 5'-untranslated sequences. Multiple transcription initiation sites were observed by primer extension experiment. The promoter function was examined by using luciferase as a report gene in transfected human vascular smooth muscle cells.