  We consider in more detail the role of D0-branes as instantons in the
construction of SU(N) Super Yang-Mills and Super QCD theories in four
space-time dimensions with D4, D6 and NS-branes. In particular, we show how the
D0-branes describe both the exact and constrained instantons and reproduce the
correct pattern of lifting of zero modes on the various branches of these
models.
