The effects of simulated acid rain on two soybean [Glycine max (L.) Merrill] cultivars were studied in field experiments in central Illinois. The cultivars,‘Amsoy 71’and‘Williams 82′, were shielded from ambient precipitation and treated twice weekly with applications of 1.05 cm of one of six simulated rain treatments which ranged in pH from 5.6 to 3.0. Each treatment was replicated 12 times in 1983, nine times in 1984, and six times in 1985. Measurements were taken for plant height, chaff dry weight, plant population, lodging, pods/plant, seeds/plant, seeds/pod, mass/seed, and number of low pods. There were small but significant (α= 0.10) effects of treatment acidity in some years for some of the parameters measured. For Amsoy 71, in one of three years, seeds/plant, seeds/pod, and chaff dry weight were reduced by increasing acidity of the simulated rain. In general, Amsoy 71 plants subjected to the more acidic treatments were shorter and had lower lodging in the second and third years of the experiments. For Amsoy 71 there were no significant linear contrasts for the effect of simulated acid rain on plants/ha, mass/seed, and protein concentration of the seed. For Williams 82 there was a small but significant trend for increased seed oil with decreasing pH in 1984 only. For this cultivar there were no significant linear contrasts for the effect of simulated acid rain on plants/hectare, plant height, lodging score, chaff dry weight, low pods, pods/plant, seeds/plant, seeds/pod, or mass/seed. Where changes in either cultivar occurred, the magnitude of these changes over the entire pH range studied was generally 6% or less. Not only was the magnitude of the responses minimal, but the response to simulated acid rain was not consistent between cultivars or in some cases within cultivars from year to year. The response to stimulated acid rain was also small when compared with the potential effect of other stresses such as drought, ozone, disease, insects, and weeds on soybean yield and growth parameters.