Paralysis of domestic stock by the paralysis tick Ixodes holocyclus is chiefly a disease of young animals (especially calves) and of non-habituated stock introduced into tick-infested country in spring. The tick has a wide host range, but its principal hosts are bandicoots. The tick has one generation per year and the adult female, which causes almost all paralysis, is abundant in spring and early summer and occurs most commonly in overgrown or regrowth country where bandicoots are abundant. The distribution and behavior of the long and the short-nosed bandicoots are reviewed. The number of ticks required to induce paralysis in cattle and the protection from paralysis afforded by prior experience of the tick are discussed.