Two soybean, (Glycine max (L.) Merr.) cultivars, Essex and Williams, were grown in the field for 6 consecutive seasons under ambient and supplemental levels of ultraviolet-B radiation to determine the potential for alterations in yield or seed quality with a reduction in the stratospheric ozone column. The supplemental UV-B fluences simulated a 16 or 25% ozone depletion. The data presented here represent the first field experiment conducted over multiple seasons which assesses the effects of increased UV-B radiation on seed yield. Overall, the cultivar Essex was found to be sensitive to UV-B radiation (yield reductions of 20%) while the cultivar Williams was tolerant. However, the effectiveness of UV-B radiation in altering yield was strongly influenced by the seasonal microclimate, and the 2 cultivars responded differently to these changing factors. Yield was reduced most in Essex during seasons in which water availability was high and was reduced in Williams only when water was severely limiting. The results of the experiments demonstrate the necessity for multiple-year experiments and the need to increase understanding of the interaction between UV-B radiation and other environmental stresses in order to assess the potential consequences of stratospheric ozone depletion.