The soybean aphid, Aphis glycines, and the soybean cyst nematode, Heterodera glycines, are major pests of soybean in the north central United States. Combined, these pests may account for 20 to 50% of yield reductions in a soybean crop. Only limited information is available concerning the interactions of these two pests in soybean. During the summers of 2006 and 2007, we conducted a field experiment near Urbana, Illinois and evaluated the impact of resistant and susceptible soybean varieties on the development and reproduction of both pests in the presence of each other. We also determined how the interaction of both pests affected yields of susceptible and resistant soybean varieties. Soybean plants grown within caged microplots were infested with soybean aphids (10 aphids per cage during full pod stage R4 in 2006 and full bloom stage R2 in 2007) and, twice each week, the number of aphids on three plants per cage was determined. Research conducted in 2006 showed aphid populations in one soybean cultivar (LD05-16519) increased midway through the growing season and continuing to increase until plants reached senescence. Yield was measured at the end of both growing seasons. At the conclusion of this experiment, we will assess whether current management recommendations for both pests need to be altered based upon our findings.