  We analyze data on pulsation amplitudes and phases for two $\beta$ Cephei
stars, $\delta$ Cet and $\nu$ Eri. Str\"omgren photometry and radial velocity
measurements are used simultaneously to obtain constraints on mean parameters
of the stars and identification of the excited modes. The inference about the
radial mode order and mean star parameters is based on comparison of certain
complex parameter, $f$, determined from data, with its counterpart derived from
linear nonadiabatic modelling of stellar oscillations. The theoretical $f$
values are very sensitive to the adopted opacity data. In our modelling we rely
on the data from OPAL and OP projects. Significant differences were found. New
seismic models of $\nu$ Eri were constructed with both the OPAL and OP
opacities.
