  In this work we consider the evolution of a massive scalar field in
cylindrically symmetric space-times. Quasinormal modes have been calculated for
static and rotating cosmic cylinders. We found unstable modes in some cases.
Rotating as well as static cosmic strings, i.e., without regular interior
solutions, do not display quasinormal oscillation modes. We conclude that
rotating cosmic cylinder space-times that present closed time-like curves are
unstable against scalar perturbations.
