  Recently, peculiar velocity measurements became available for a new sample of
galaxy clusters. From an accurately calibrated Tully-Fisher relation for spiral
galaxies, we compute the rms cluster peculiar velocity and compare it to the
linear theory predictions of COBE-normalized low-density and open CDM models
(LambdaCDM and OCDM, respectively). Confidence levels for model rejection are
estimated using a Monte Carlo procedure to generate for each model a large
ensemble of artificial data sets. Following Zaroubi et al. (1997), we express
our results in terms of constraints on the (Omega_0,n_pr,h) parameter space.
Such constraints turn into sigma_8 Omega_0^{0.6}=0.50^{+0.25}_{-0.14} at the
90% c.l., thus in agreement with results from cluster abundance. We show that
our constraints are also consistent with those implied by the shape of the
galaxy power spectrum within a rather wide range for the values of the model
parameters. Finally, we point out that our findings disagree at about the
3sigma level with respect to those by Zaroubi et al. (1997), based on the Mark
III catalogue, which tend to prefer larger Omega_0 values within the CDM class
of models.
