This study evaluated the diversity and abundance of existing natural enemies of soybean aphid, Aphis glycines L., under field conditions in New York State, with emphasis on entomopathogenic fungi. In 2003, five soybean fields were occasionally sampled to estimate abundance and species composition of entomopathogenic fungi. During 2004, five soybean fields and adjacent buckthorn were sampled weekly. Seven species of aphid pathogenic fungi were found, including Pandora neoaphidis (Remaud. et Henn.) Humber, Conidiobolus thromboides Drechsler, Entomophthora chromaphidis Burger et Swain, Pandora sp., Zoophthora occidentalis (Thaxter) Batko, Neozygites fresenii (Now.) Remaud. et Keller, and Lecanicillium lecanii, (Zimm.) Gams et Zare. P. neoaphidis was the most abundant species, causing 84% infection in an outbreak aphid population in 2003, after which the aphid population crashed. In 2004, we found the first aphids with fungal infections in late June to midJuly. Mycosis was strongly associated with aphid density, especially during increasing aphid populations. In agreement, epizootic levels of infection were associated with subsequent declines in aphid populations. There was variability among fields; in three of five fields sampled in 2004, the chances for infection were more than five times higher than in the other two fields. High infection levels were found on aphids on buckthorn over 3 wk in autumn. Three species of aphidiid parasitoids from A. glycines were documented: Aphidius sp. and two Praon species. Both genera were the first records from A. glycines in the United States. Coccinellids were the most abundant predator, followed by syrphids and cecidomyiids, whereas anthocorids and chrysopids were less common.