We collected and examined teeth from 3406 red foxes (Vulpes vulpes) collected in Ontario, Canada, from 1978 to 1986, prior to large scale rabies vaccine baiting. We found tetracycline-like fluorescence in five (0.2%) of the samples. Also, we observed similar fluorescences in five (0.4%) of 1103 striped skunks (Mephitis mephitis) and in six (0.8%) of 744 raccoons (Procyon lotor). The low prevalence of such marks would not appear to invalidate the use of tetracycline as a marking agent in vaccine baiting trials.