  In a recent paper (M. Bostrom and Bo E. Sernelius, Phys. Rev. Lett. 84, 4757
(2000)) the combined effect of finite conductivity and finite temperature on
the Casimir force is analyzed, and significant deviations from other
theoretical results and a recent experiment are obtained.
  In this Comment, I show that the extrapolation to zero frequency is incorrect
because the authors have neglected that the wavenumber and frequency of the
electromagentic mode must simultaneously appraoch zero
