The effects of the distal nerve degeneration on the regeneration of the collateral sprouts from the proximal nerve stump have been examined. The delayed cross-suture anastomosis technique was used in which the tibial nerve was denervated for 0-8 weeks before cross-suture of the freshly axotomized common peroneal and chronically denervated TIB nerve stumps. There was a remarkable decreasing of the regenerated myelinated axons number after the distal nerve suffered 8 weeks deterioration, suggesting that short-term denervation did not affect the collateral sprouts regeneration but more prolonged denervation profoundly reduced collateral sprouts regenerated in the distal nerve stump.