This paper deals with leader-following formation control of a group of wheeled mobile robots (WMRs) when the leadership alternates among the robots of the group. In the problem presented here, firstly a scout robot is used to search for a path in a previously unknown environment with static obstacles. The path found by this scout is used as a reference for the leader of the multi-robot formation. As the group follows the trajectory preserving the formation, whenever any robot in the formation is closer than a limit threshold distance from an obstacle, this robot assumes the leadership. So the new leader must adequate its position to the reference trajectory, and, as a result of the formation control, the position of the whole group is also adjusted. This way, the whole group navigates avoiding collisions with obstacles. The mobile robots exchange their position information among themselves according to a pre-specified communication directed graph (digraph). A different digraph is defined for each robot as a leader. Simulation results are presented for the formation control applied on this scenario. © 2011 IFAC.