Experimental evidence suggests that reinnervation of the distal stump of a transected nerve may occur if the former is coapted end-to-side to the trunk of an adjacent nerve. Axonal regeneration occurs by collateral sprouting of healthy donor nerve axons, induced by neurotrophic factors. End-to-side neurorrhaphy can provide satisfactory functional recovery for the recipient nerve, without any deterioration of the donor nerve function. Various experimental models have been proposed in order to increase regeneration efficiency after end-to-side neurorrhaphy. End-to-side neurorrhaphy has already been used in the clinical practise, but there are still some issues that have not been completely clarified yet: (i) the origin of regenerating axons, (ii) collateral sprouting molecular mechanisms, and (iii) the degree of donor nerve axotomy needed for motor functional recovery. The results of experimental studies trying to investigate these parameters are briefly discussed in this review article.