Spargana of Spirometra erinacei infect many vertebrate species, but severe disease from sparganosis has been reported from few host species. Information on the effects of this common, introduced tapeworm of cats on Australian frogs is lacking. Our survey to detect significant diseases in free-ranging amphibians in eastern Australia between 1993 and 2000 revealed that infection with spargana (plerocercoids) of S. erinacei occurred in 12/243 (4.9%) sick frogs. Infections occurred in skeletal muscle and subcutis, especially the thighs, of large adults of Litoria caerulea, Litoria aurea, Litoria gracilenta, and Litoria peronii. Three frogs were also infected in the coelomic cavity. Heavy burdens in seven frogs were associated with poor body condition and debilitating lesions, whereas lighter infections in five sick frogs were considered likely to be incidental to other diseases. In severe infections, a large proportion of thigh muscle was replaced with spargana and various amounts of fibrosis, and some frogs also had myonecrosis, granulomatous inflammation, hemorrhage, and skin ulceration. Concurrent infections were common. Our findings suggest sparganosis is one of a few currently recognized serious diseases affecting free-ranging frogs in Australia.