An epizootic of fibropapillomas in green turtles Chelonia mydas (Reptilia: Testudines: Cheloniidae) has occurred throughout the Caribbean since the mid-1980s. Similar epizootics in Hawaii and Florida began 5 years earlier. All may be part of a panzootic. The 125 Caribbean cases greatly expand the known range of these epizootics. All the tumors we examined had spirorchiid (Digenea) eggs. Few turtles we examined with tumors were emaciated. Additional tumors quickly erupted in some captive turtles, whereas tumors of others remained unchanged for 1 year. The turtle leech Ozobranchus branchiatus (Hirudinea: Ozobranchidae) was associated with only three green turtles with fibropapillomas.