It is well known that earthworms (Annedlida, Oligochaeta) have an important influence on organic matter decomposition, soil fertility, and soil structure. Their activity affects soil hydrology and stability, nutrient availability, and the activity of other soil organisms, thereby contributing to primary productivity in terrestrial ecosystems. The species found most commonly in temperate agroecosystems, particularly in North America, are members of the family Lumbricidae, a group with 16 genera and about 300 species worldwide (Lee 1985). Our discussion focuses on the taxonomic and functional diversity of lumbricid earthworms in agroecosystems, reports on how agricultural practices influence earthworm diversity, and finally provides information on how earthworm diversity may influence agroecosystem functions in temperate regions.