  We present a survey of nonradial mode properties in evolutionary sequences of
RR Lyrae star models. Attention is focused on the modes that may be driven by
the opacity mechanism and on those that may be excited as a consequence of the
1:1 resonance with the radial pulsation.
  Qualitatively, all the models share the same properties of the nonradial
modes. At the quantitative level, the properties are to a large extent
determined by the radial mode periods. There is only weak dependence on the
star metallicity and no apparent dependence on the evolutionary status, that is
on the helium exhaustion in the convective core.
  In the whole range of RRab and RRc star parameters we find unstable nonradial
modes driven by the opacity mechanism. An instability of radial pulsation to a
resonant excitation of nonradial oscillations is also a common phenomenon in
both types. We discuss a possible role of nonradial modes in amplitude
modulation observed in certain RR Lyrae stars.
