The tapeworm Spirometra theileri (Baer, 1925) n. comb., obtained as pleroccrcoids from a wart hog in Tanzania, has been maintained in the laboratory; adults in dogs, and larval stages in Cyclops and then rodents. The species differs physiologically and biologically from those described from other parts of the world in the cyclical production of eggs in dogs, inability of the procercoids to infect amphibia or reptiles, and the lack of any parasite-induced weight gain in mice, rats or hamsters.