  In this paper we show how to compute in a consistent way nucleation rates in
field theory at finite temperatures, with metastable vacuum. Using the
semiclassical approach in field theory at finite temperature we show that the
prefactor term can be calculated explicitly (in the thin-wall approximation)
and that the same provides exponential finite temperature quamtum corrections
to nucleation rates, when fluctuations around the bubble field configuration
are considered.
