  In this note we present an explicit procedure for the regularization of tree
level amplitudes involving discrete states, using open string field theory. We
show that there is a natural correspondence between the discrete states and
off--shell states, later acting as a regularized version of the former. A
general off-shell state corresponds to several physical states. In order to
obtain the well--defined $S$ matrix elements one has to choose representatives
close but not equal to the desired values of external momenta. The procedure
renders finite all $4$-point amplitudes with an even number of (naively)
divergent channels even after the regularization is removed. The rest of the
amplitudes can be defined by means of such regularization.
