Thrombospondin1 (TSP1) is a known antiangiogenic factor, but its possible alteration during the early stages of diabetic retinopathy has not been explored yet. The present study sought to investigate the expression of TSP1 using a model of streptozotocin (STZ) induced diabetes in the rat. Diabetes was induced in male SD rats by an intraperitoneal injection of STZ. Age matched animals served as control. 2 months after the onset of diabetes, the expression of TSP1 mRNA was quantified in retinal tissue by quantitative real time reverse transcription-polymerase chain reaction (RT-PCR) respectively. The locations of TSP1 normal and diabetic retinas were also established by immunohistochemistry. 2 months after the onset of diabetes, retinal TSP1 concentrations were significantly increased in the diabetic rats compared with control rats. Diabetes caused the upregulation of TSP1 expression in the layers of the retina 2 months after the induction of diabetes. The upregulation of TSP1 in retinas of diabetic rats suggests a role in experimental diabetic retinopathy. Further studies should address the possible involvement of the TSP1 in the pathophysiology of diabetic retinopathy.