Background Hypoxia-inducible factor 1 (HIF-1), a transcription factor, is overexpressed in common human cancers and their metastases. This study aimed at determining the expression levels of HIF-1α and vascular endothelial growth factor (VEGF) in SW480 cells and in colorectal adenocarcinoma tissue and ascertaining whether HIF-1α and VEGF play important roles in tumor angiogenesis. Methods HIF-1α mRNA expression was analyzed using in situ hybridization and RT-PCR. HIF-1α and VEGF protein were detected in SW480 cells and colorectal adenomas and adenocarcinomas by immunohistochemistry using streptavidin/peroxidase (SP). Western blot was used to detect HIF-1α protein extracted from SW480 cells. Microvessel density (MVD) in colorectal carcinomas was determined by anti-CD34 immunostaining in colorectal carcinomas. Results Optical density values representing HIF-1α mRNA expression levels were found to be significantly higher in SW480 cells in hypoxic conditions than in cells under normoxic conditions (P