  Using existing experimental information from K, B and D decays as well as
electroweak precision tests and oblique parameters, we provide constraints and
correlations on the parameters of the 4X4 mixing matrix for the Standard Model
with four generations (SM4). We emphasize that some correlations amongst the
parameters have important repercussions for key observables. We work with a
particular representation of this matrix which is highly suited for extracting
information from B-decays. Implications of the resulting constraints for time
dependent and semileptonic CP asymmetries for $D^0$, $B^0$ and for $B_s$ are
also given. While we show that the semi-leptonic asymmetries may be
significantly enhanced in SM4 over the SM, there are important constraints and
correlations with other observables. In this context we suggest that existing
data from B-factories taken on $\Upsilon (4S)$ and $\Upsilon (5S)$, and in the
relevant continuum be used to constrain the semi-leptonic asymmetries for
$B_d$, $B_s$ as well as their linear combination. Of course, the data from the
Tevatron and LHCb experiments can provide non-trivial tests of SM4 as well.
