To reveal whether neuropeptides and cytokines affect the pathogenesis of tennis elbow, expressions of substance P, calcitonin gene-related peptide, interleukin 1 alpha, and transforming growth factor beta1 at the origin of the extensor carpi radialis brevis muscle were investigated in patients with tennis elbow (n = 10). Innervation in the origin was determined with use of the protein gene product 9.5. Substance P-like immunoreactivity and calcitonin gene-related peptide-like immunoreactivity were observed in the nerve fibers around small vessels without apparent infiltration of inflammatory cells. Cells showing positive interleukin 1 alpha or transforming growth factor beta1 immunoreactivity were noted in small vessels and the dense collagen meshwork in 5 of 10 cases. The results suggested that these neuropeptides and cytokines might promote inflammation and stimulate proliferation and matrix synthesis of fibroblasts, contributing to the pathology of tennis elbow.