The purpose of this study was to investigate neovascularization and the expression of vascular endothelial growth factor (VEGF) in patients with diabetic frozen shoulders. Eleven patients with diabetic frozen shoulders underwent arthroscopic lysis of adhesions, and we observed the reported findings. VEGF expression was determined by immunohistochemistry and Western blot analysis, and the density of vessels was evaluated based on CD34 immunoreactivity by use of samples of the synovial tissue. For the control group, we took 5 samples of synovium from patients undergoing shoulder arthroscopy. The arthroscopic findings showed hyperemia of the synovial tissue in all cases of diabetic frozen shoulder. This synovium showed stronger immunostaining to VEGF (P = .010) and CD34 (P = .011) than the control synovial tissue. Western blot analysis also showed a stronger VEGF intensity than in the control group. We postulate that VEGF is synthesized and secreted in the synovium of diabetic frozen shoulders and VEGF may have some role in the pathogenesis and neovascularization of frozen shoulders in diabetic patients.