The influence of enhanced UV-B radiation (280-320 nm) on wheat (Triticum aestivum cv. 'Florida 301') yield, and disease incidence and severity was investigated for two growing seasons under field conditions. Three levels of UV-B enhancement, simulating 8,12 and 16% stratospheric ozone reduction, were employed during 1982, and two levels of UV-B radiation enhancement, simulating 12 and 16% ozone depletion, were used during 1983. At each level of UV-B enhancement during 1982, no significant direct effect upon yield was observed. However, in 1983, there was an indication that UV-B radiation was interacting with other parameters because there was a significant bimodal response on plant and seed dry weights. During 1983, specific small plots were used to test for leaf rust severity on a resistant and a susceptible cultivar. Leaf rust on the resistant cultivar 'Florida 301' decreased with plant age, but control and UV-treated plants were not different.