  The dynamics of polymer decompression, i.e., a process from compressed,
compact state to the relaxed swoll en conformation, can be formally described
as a {\it nonlinear diffusion}. We discuss here two basic examples: (i) the
expansion, or unfolding from a compact state, and (ii) the ejection of pressed
polymer through a pore. The problem can be solved exactly for the case (i), but
not for the latter. Even in such situations, a scheme called {\it uniform
approximation} is shown to be useful to get a physical insight involved. Its
application to the case (ii) is able to account for conflicting numerical data
in a consistent way.
