  In this paper we investigate gravitational perturbations of a regular black
hole, particularly Bardeen solution. Such system is solution of Einstein
equations that do not have a singularity at the origin of the radial symmetry.
However it still have events horizons depending on the values of the
characteristic parameters of the solution. When a black hole is perturbed, it
oscillates. It gives rise to damped vibrating modes which are known as
quasinormal modes. It is calculated the quasinormal frequencies of a regular
black hole using the third order WKB approximation for gravitational
perturbations. The results are presented in tables I, II and III.
