  The influence of Coulomb interaction on the electron transport through
molecular wires is studied in the regime of incoherent tunneling. In the limit
of strong Coulomb repulsion, the current for spinless electrons is determined.
It is shown that the voltage profile along the wire crucially influences the
dependence of the current on the wire length. Upon inclusion of the spin degree
of freedom one finds a blocking effect which depends both on the interaction
strength and on the population of the wire. For finite Coulomb interaction, the
temperature dependence of the blocking is studied and it is shown that several
regimes with different blocking strength may exist.
