Charm system tests of CPT with FOCUS

We discuss a search for CPT violation in neutral charm meson oscillations. The data come from the Fermilab fixed-target experiment FOCUS. While flavor mixing in the charm sector is predicted to be small by the standard model, it is still possible to investigate CPT violation through study of the proper time dependence of the asymmetry in right-sign decay rates for D0 and D0-bar. Using present limits for D0-D0-bar mixing we infer bounds on charm CPT violation using data from FOCUS.