  We consider aspects of instanton dynamics in the large-N limit using the
AdS/CFT duality for D0/D4 bound states. In the supergravity picture of wrapped
D0-brane world-lines on D4-branes, we find the single-instanton measure and
discuss its dependence on compactification finite-size effects, as well as its
matching to perturbative results. In the non-supersymmetric case, the same
dynamical effects that produce the theta-angle dependence perturbatively in
1/N, render the instantons unstable, although approximate instantons of very
small size still exist. The smeared D0/D4 black-brane supergravity solution can
be interpreted as dual to a field theory configuration of an instanton
condensate in the vacuum. In this case, we derive a holographic relation
between the bare theta angle and the topological charge density of the
instanton condensate.
