In the frame-work of the isotropic elastic theory, we have recently shown that it is possible to derive, from the total interaction energy between the partials, a simple analytic solution for the equilibrium configuration of the Lomer-Cottrell dislocation. We have established, contrary to what is generally believed, that it should be asymmetric. By using the same procedure, we reconsider in this paper the equilibrium configurations of the extended dislocations barriers (B2-B6) in the face centred cubic (f.c.c.) structure. As for the Lomer-Cottrell dislocation, the equilibrium configuration of the B2 barrier must be also asymmetric. The equilibrium shapes obtained for the other barriers (B3-B6) are found to be in good agreement with all previous predictions.