After background information about pathologic findings, this review focuses on the cytokine response in the pathogenesis of polymyositis and dermatomyositis. Cytokines are important mediators of the immune response and play a key role in these diseases by acting on inflammatory immune cells, muscle cells, and vessel cells. Various cytokines are found in myositis samples, in particular interleukin-1 and tumor necrosis factor-alpha, which are associated with the migration, differentiation, and maturation of inflammatory cells. Recent advances indicate that the muscle cell itself could participate in the inflammatory process. Cytokines promote changes in muscle metabolism resulting in a self-sustaining inflammatory response. Accordingly, cytokines may represent new targets for therapies.