We are investigating the impact of living mulches on beneficial and pest insects as part of a long-term study on the addition of living mulches to annual crop production. In 2004, we observed a greater number of soil and foliar-based predators on soybeans (Glycine max L.) grown with a living mulch comprised of either alfalfa (Medicago sativa L.) or kura clover (Trifolium ambiguum M.B.). Abundance of aphidophagous predators was greatest in soybean planted with a living mulch in June, when soybean aphids (Aphis glycines Matsumura, Hemiptera: Aphididae) are immigrating from their overwintering host. In 2005, we are testing the hypothesis that natural enemy abundance will increase and soybean aphid establishment and population growth will decline when soybeans are grown within a living mulch of alfalfa. Replicated plots (4 replications, 30 m wide and 27 m long) of soybean were planted with and without a fall-sown alfalfa. We are measuring natural enemy abundance with yellow sticky cards, pitfall traps and sweep-nets on a regular basis from May to September. To measure the impact of natural enemies on soybean aphid, we are employing natural enemy exclusion cages in soybeans grown with and without alfalfa. In June, we will artificially infest caged and uncaged plants with soybean aphid. Natural enemy sampling in May 2005 revealed a nearly 2-fold increase in soybean grown with alfalfa. By comparing the rate of soybean aphid predation in soybeans grown with and without alfalfa we will determine if this enhancement of natural enemies leads to pest suppression.