AbstractInsulin-like growth factor I (IGF-I; somatomedin C) has previously been demonstrated, with immunohistochemical methods, to accumulate locally at the site of trauma of an injured peripheral nerve. In the experiments reported here a Y-shaped silicone-chamber system was used to test if local infusion of IGF-I had supportive effects on nerve regeneration. The proximal end of a cut sciatic nerve was inserted into one channel of the Y-shaped chamber and the length and growth direction of the regenerating myelinated axons were evaluated after 1 month. When IGF-I (250μ;g/ml 0.5μ;l/h) was infused into one channel by an osmotic pump, the length of the regenerating axons increased significantly compared to the control groups with no IGF-I added. In some instances the regenerating axons grew towards the osmotic pump. It is concluded that local infusion of IGF-I at appropriate concentration promotes regeneration of a peripheral nerve. It exerts a neuronotrophic but not a clear chemotactic effect.