We present evidence for a decline in the population of the American eel (Anguilla rostrata) from several widely distributed regions of North America from 1984 to 1995. Trends in population indices from commercial catch data, upstream passage counts, and seine, trawl, and electrofishing surveys were analyzed and found to be either not significant or significantly negative. Explanations for this decline, whether natural or anthropogenic, are unknown, due to variation and incompleteness in abundance data, and incomplete knowledge of eel life history, ecology, and population dynamics. A number of potential factors may be contributing to the decline, including (in alphabetical order): barriers to migration, habitat loss and alteration, hydro turbine mortality, oceanic conditions, over-fishing, parasitism, and pollution. The paucity of life table data associated with the unconventional life history characteristics of anguillid eels (catadromy, panmixis, semelparity, high age at maturity, wide geographi...