  Possibilities for observing signals of CPT and Lorentz violation in the
spectroscopy of hydrogen and antihydrogen are considered. We show that
transitions between the c and d hyperfine sublevels in the 1S state can exhibit
theoretically detectable effects that would be unsuppressed by powers of the
fine-structure constant. This transition may therefore offer some advantages
over 1S-2S two-photon spectroscopy.
