  We discuss the exact renormalization group or flow equation for the effective
action and its decomposition into one particle irreducible N point functions.
With the help of a truncated flow equation for the four point function we study
the bound state problem for scalar fields. A combination of analytic and
numerical methods is proposed, which is applied to the Wick-Cutkosky model and
a QCD-motivated interaction. We present results for the bound state masses and
the Bethe-Salpeter wave function. (Figs. 1-4 attached as separate uuencoded
post-script files.)
