Quantitative RT-PCR assay detecting the transcriptional induction of vascular endothelial growth factor under hypoxia. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) assay was used to examine the induction of vascular endothelial growth factor (VEGF) transcript in human osteosarcoma cells, MG-63, under hypoxic culture condition. Using this assay system, the expression of VEGF mRNA was estimated eight-fold higher when cells were cultured under hypoxic condition. Transcription level of hypoxanthine phosphoribosyl transferase (HPRT) mRNA was also examined as an internal control. HPRT mRNA level under hypoxia was reduced to one fourteenth. Secretion of VEGF into the cell culture medium was implied by its stimulating activity on the growth of mouse vascular endothelial cultured cells in vitro.