Despite their insignificant form and size, ticks are one of the most readily recognized groups of arthropods in Canada. They are repugnant to most people not only because of their blood-feeding habits, but some species may cause paralysis or serve as reservoirs and vectors of a remarkable variety of pathogens, including viruses, rickettsiae, bacteria, protozoans and spirochaetes. in Canada, these pathogens include the causative agents of Lyme borreliosis, relapsing fever, tularemia, Rocky Mountain spotted fever, Q fever, Colorado tick fever, Powassan encephalitis, and perhaps others, some of which afflict wild and domesticated animals as well as humans, leading to highly pervasive medico-veterinary and economic issues. An important step is correct identification of the offending entity, which with ticks may be any of the active immature or adult forms.