Precision Studies of Relativity in Electrodynamics

In this contribution to the proceedings of the 2002 Workshop for Fundamental Physics in Space, a discussion of recent work on astrophysical and laboratory tests of Lorentz symmetry in electrodynamics is presented. Stringent constraints are placed on birefringence of light emitted from galactic and extragalactic sources. The prospect of precision clock-comparison experiments utilizing resonant cavities are considered.