Vascular endothelial growth factor (VEGF) is an apparently endothelial cell-specific mitogen that is structurally related to platelet-derived growth factor. By Northern blot and protein analyses, we show that VEGF is produced by cultured vascular smooth muscle cells. Analysis of VEGF transcripts in these cells by polymerase chain reaction and cDNA cloning revealed three different forms of the VEGF coding region, as had been reported in HL60 cells. The three forms of the human VEGF protein chain predicted from these coding regions are 189, 165, and 121 amino acids in length. Comparison of cDNA nucleotide sequences with sequences derived from human VEGF genomic clones indicates that the VEGF gene is split among eight exons and that the various VEGF coding region forms arise from this gene by alternative splicing: the 165-amino-acid form of the protein is missing the residues encoded by exon 6, whereas the 121-amino-acid form is missing the residues encoded by exons 6 and 7. Analysis of the VEGF gene promoter region revealed a single major transcription start, which lies near a cluster of potential Sp1 factor binding sites. The promoter region also contains several potential binding sites for the transcription factors AP-1 and AP-2; consistent with the presence of these sites, Northern blot analysis demonstrated that the level of VEGF transcripts is elevated in cultured vascular smooth muscle cells after treatment with the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate.