  Here we show a hidden regularity result for nonlinear wave equations with an
integral term of convolution type and Dirichlet boundary conditions. Under
general assumptions on the nonlinear term and on the integral kernel we are
able to state results about global existence of strong and mild solutions
without any further smallness on the initial data. Then we define the trace of
the normal derivative of the solution showing a regularity result. In such a
way we extend to integrodifferential equations with nonlinear term well-known
results available in the literature for linear wave equations with memory.
