β Cephei stars are early B-type stars which show periodic variations of luminosity, radial velocity and line profiles. They have periods between 2 and 7 hr. Their variability is now believed to be caused by the classical κ-mechanism operating in the heavy-element ionization zones. Many of the β Cephei stars are multimode pulsators, and radial as well as nonradial pulsation may occur. Advances in the last few years in both the observational and theoretical studies of multiple pulsation modes of δ Scuti stars have reached the stage that realistic comparisons of the results and examination of predictions can be carried out (Breger et al. 1998; Stankov et al. 1999). We now want to apply those asteroseismological methods to the much hotter β Cephei stars.