  We discuss the calculation of one-loop effective actions in Lorentzian
spacetimes, based on a very simple application of the method of steepest
descent to the integral over the field. We show that for static spacetimes this
procedure agrees with the analytic continuation of Euclidean calculations. We
also discuss how to calculate the effective action by integrating a
renormalization group equation. We show that the result is independent of
arbitrary choices in the definition of the coarse-graining and we see again
that the Lorentzian and Euclidean calculations agree. When applied to quantum
gravity on static backgrounds, our procedure is equivalent to analytically
continuing time and the integral over the conformal factor.
