  We give necessary and sufficient conditions for a polynomially bounded
o-minimal expansion of a real closed field (in a language of arbitrary
cardinality) to be $\aleph_{\alpha}$-saturated. The conditions are in terms of
the value group, residue field, and pseudo- Cauchy sequences of the natural
valuation on the real closed field. This is achieved by an analysis of types,
leading to the trichotomy. Our characterization provides a construction method
for saturated models, using fields of generalized power series.
