1. A routing method in an ad hoc network between a source node (S) and a destination node (M), wherein, to guarantee a required quality of service level between the source node and the destination node, the method comprises the steps of: in a preliminary step: (a) evaluating at each node of the network a quality of service level for each connection between said node and the neighbor nodes; (b) establishing a cost function (F g ) representative of the cost in terms of resources necessary to guarantee a given quality of service level on a connection between a node and each of the neighbor nodes; the source node (S) sending a route request to the network, said request containing said required quality of service level and an initial value of said cost function (F g ); a node receiving a route request sent by a neighbor node then: (a) refusing said request if said node is not able to guarantee said required quality of service level; (b) sending over the network a route request containing said required quality of service level and a value of said cost function combining a value of the cost function received from a previous neighbor node and a value of the cost function calculated on a connection with a neighbor node; the destination node (M) sending a route response step by step to the source node (S) containing the cumulative value of said cost function (F g ) corresponding to a route formed by successive connections between the source node (S) and the destination node (M); and the source node choosing the route between the source node (S) and the destination node (M) having the best cumulative cost function.