This work is concerned with the initial boundary value problem for a nonlinear viscoelastic Petrovsky wave equation utt +, 2u ,Z t 0 g(t ,, ), 2u(,)d,, , ut , , utt + utjutjm, 1 = ujujp, 1: Under suitable conditions on the relaxation function g, the global ex-istence of solutions is obtained without any relation between m and p. The uniform decay of solutions is proved by adapting the perturbed energy method. For p > m and su, cient conditions on g, an unbound-edness result of solutions is also obtained.