  Four 4-dimensional Painlev\'e-type equations are obtained by isomonodromic
deformation of Fuchsian equations: they are the Garnier system in two
variables, the Fuji-Suzuki system, the Sasano system, and the sixth matrix
Painlev\'e system. Degenerating these four source equations, we systematically
obtained other 4-dimensional Painlev\'e-type equations. If we only consider
Painlev\'e-type equations whose associated linear equations are of unramified
type, there are 22 types of 4-dimensional Painlev\'e-type equations: 9 of them
are partial differential equations, 13 of them are ordinary differential
equations. Some well-known equations such as Noumi-Yamada systems are included
in this list. They are written as Hamiltonian systems, and their Hamiltonians
are neatly written using Hamiltonians of the classical Painlev\'e equations.
