Although reimplantations are very well defined operations, the indications for emergency free flaps and the management of nerve injuries are much less so. Using several examples, the authors define the conditions in which a free flap is justified and the most useful procedures for nerve repair. An emergency free flap should constitute the best solution, with a reasonable chance of success, without compromising other possibilities of reconstruction in the event of failure. The authors present the three situations observed in the case of nerve lesions: clean nerve sections, nerve defects, cases with an unclear diagnosis and cases in which the conditions are unsuitable for immediate permanent repair.