  We present quantum Monte Carlo results for the Hubbard model on a ladder
using the re-structuring method which employ eigenstates of two-site system on
a rung to construct a complete set. From technical reasons we concentrate on
the case in which the hopping along the leg is much less than the hopping on
the rung. We observe the ground state of the half-filled system is made of
singlet-like states described in this paper and its first excited state
contains one triplet rung. When the system is lightly doped states composed of
an electron and a hole appear on some rungs. We find very few hole-pairing on
the rung upon doping up to the quarter-filled case.
