  We present a theoretical analysis of signals for CPT and Lorentz violation in
g-2 and charge-to-mass-ratio experiments on electrons and positrons in Penning
traps. Experiments measuring anomaly frequencies are found to be the most
sensitive to CPT violation. We find that the conventional figure of merit for
CPT breaking, involving the difference of the electron and positron g factors,
is inappropriate in this context, and an alternative is introduced. Bounds of
approximately one part in 10^{20} are attainable.
