  Motivated also by recent revival of interest about metastable string states
(as cosmic strings or in accelerator physics), we study the decay, in presence
of dimensional compactification, of a particular superstring state, which was
proven to be remarkably long-lived in the flat uncompactified scenario. We
compute the decay rate by an exact numerical evaluation of the imaginary part
of the one-loop propagator. For large radii of compactification, the result
tends to the fully uncompactified one (lifetime T = const M^5/g^2), as
expected, the string mainly decaying by massless radiation. For small radii,
the features of the decay (emitted states, initial mass dependence,....)
change, depending on how the string wraps on the compact dimensions.
