  We study the interplay between Coulomb blockade and the Kondo effect in
quantum dots. We use a self-consistent scheme which describes mesoscopic
devices in terms of a collective phase variable (slave rotor) and quasiparticle
degrees of freedom. In the strong Coulomb blockade regime, we recover the
description of metallic islands in terms of a phase only action. For a dot with
well-separated levels, our method leads to the Kondo effect. We identify the
regime where a crossover between the Coulomb blockade regime at high
temperatures and the formation of a Kondo resonance at lower temperature takes
place. In addition, we find that for a dot with many overlapping resonances, an
{\it inverse crossover} can take place. A Kondo resonance which involves many
levels within the dot is first formed, and this coherent state is suppressed by
correlation effects at lower temperatures. A narrower Kondo resonance, due to a
single level in the dot can emerge at even lower temperatures.
