  The experimentally observed difference of superconducting critical
temperature $T_{c}$ in hole-doped cuprates is studied by using an extended
interlayer coupling model for layered d-wave superconductors. We show that the
change of the maximum $T_{c}$ from series to series is determined by the next
nearest neighboring hopping $t^{\prime}$, while the difference of the maximum
$T_{c}$ among the compounds in a homogeneous series is controlled by the
interlayer pairing strength. Our results provide helpful guidelines in the
search for new high-$T_{c}$ superconductors.
