  We have performed the most comprehensive predictions of the temperature
fluctuations \dtt in the primeval isocurvature baryon models to see whether or
not the models are consistent with the recent data on the cosmic microwave
background anisotropies. More specifically, we computed the \dtt corresponding
to the experimental set-up by the South-Pole and the Owens Valley experiments
as well as the COBE satellite. The amplitudes of the predicted \dtt are
normalized by means of the COBE 10$^\circ$ data. The resulting constraints on
the models are presented on $n - \Omega_b$ plane in the case of
$\lambda_0=1-\Omega_b$ (flat models) and $\lambda_0=0$ (open models), where $n$
is the primordial spectral index of entropy fluctuations and $\Omega_b$ is the
present baryon density parameter.
  Our results imply that the PIB models cannot be reconciled with the current
observations for any reasonable set of cosmological parameters.
