  Analyzing IUE ultraviolet spectra of beta Cep pulsating stars we have noticed
that multiperiodic variables have a larger mean metal abundance in the
photosphere, [m/H], than monoperiodic ones. We apply statistical tests to
verify this dichotomy. We obtain that, with a large probability, the
multiperiodic beta Cep stars have greater values of [m/H]. This result is
consistent with the linear non-adiabatic theory of pulsation of early B-type
stars.
