To investigate the sequential changes of HIF-1α protein and mRNA in hypoxic bovine retinal microvessel endothelial cells. METHODS: The bovine retinal microvessel endothelial cells were cultured in normoxic and CoCl₂-induced hypoxic conditions respectively. Expressions of HIF-1α protein were measured with immunohistochemical staining, and RT-PCR was used to determine the HIF-1α mRNA. RESULTS: HIF-1α began to increase 1 hour after hypoxia, and reached the peak at 4 hour. After 16 hours, it declined significantly. Compared with the normoxic group, the expression of HIF-1α protein in the hypoxic groups had significant difference (P <0.01), and HIF-1α mRNA expression was unchanged under hypoxia. CONCLUSION: HIF-1α participates in the hypoxic procedures in retinal microvessel endothelial cells, and hypoxia induce time-dependent changes of HIF-1 α protein expression, which is not modulated on the transcription level. Analysis of HIF-1 α expression revealed a temporal and spatial changes with regard to the hyperoxic repression, indicating that HIF-1 may play a major role in the development of retinopathy of prematurity(ROP) and other ischemic retinal disorders such as diabetic retinopathy(DR).