This review describes structure, function and healing of tendinous tissue and discusses new biologically based treatment options to modulate tendon healing. The repair process after tendon rupture results in a morphologically different and biomechanically inferior structure compared to a normal tendon. The collagen fibril diameters are decreased months after the traumatic lesion and show also different phenotypes. We know that cytokines and growth factors are key components for normal tissue development and regulate wound healing processes. Some growth factors have been detected to influence tenocytes by promoting cell proliferation and matrix synthesis. Application of the adequate growth factors at certain periods during the repair process might improve the healing result after tendon rupture. However, most of these growth factors are proteins which are rapidly metabolized by the organism. Transfer of growth factor genes into tenocytes might eliminate this problem by a continuous local release of growth factors at the healing site.