A simple and computationally inexpensive approach is presented for obtaining the most sensitive imperfection mode corresponding to the maximum load factor of the stable bifurcation point. The critical point of an imperfect system is found by solving an anti-optimization problem, where the load factor is minimized with respect to the imperfection parameters and the nodal displacements under constraint on the lowest eigenvalue of the stability m a t r i x . It is shown in the examples that a minor imperfection that is usually dismissed is very important i n e v aluating the maximum load of a exible structure.