  For known gravitational lens systems the redshift distribution of the lenses
is compared with theoretical expectations for $10^{4}$~Friedmann-Lema\^\i
tre~cosmological models, which more than cover the range of possible cases. The
comparison is used for assigning a relative probability to each of the models.
The entire procedure is repeated for different values of the inhomogeneity
parameter~$\eta$ and the limiting spectroscopic magnitude~$m_{\rm lim}$, which
is important for selection effects. The dependence on these two parameters is
examined in more detail for the special cases~$\lambda_{0}=0$ and $k=0$.
  Previous results that this method is a better probe for~$\lambda_{0}$ than
$\Omega_{0}$ are confirmed, but it appears that the low probability of models
with large~$\lambda_{0}$~values found using similar methods is due to a
selection effect.
  The power of this method to discriminate between cosmological models can of
course be improved if more gravitational lens systems are found. However, our
numerical simulations indicate that a reasonable number of observed systems
cannot deliver interesting constraints on the cosmological parameters.
