Vigna unguiculata (L.) Walp. (cowpea), Glycine max (L.) Merr (soybean) and Phaseolus vulgaris (L.) (common bean) plants were exposed to UV-B radiation at above- and below-ambient levels, and their effects on growth, symbiotic performance and root concentration of metabolites were assessed. Moderately and highly elevated UV-B exposures averaging 32 and 62% above ambient had no effect on plant total dry matter, nodule number, nodule mass, nodule size, N fixed or root concentration of flavonoids, anthocyanins, soluble sugars and starch in the three species studied. However, N concentrations were markedly reduced in roots of G. max and P.vulgaris, and in leaves of P. vulgaris, which contrasted with the significant increase in stems and leaves of V.unguiculata. Below-ambient UV-B exposures averaging 22% of ambient also altered growth and metabolism of these legumes. Total plant dry matter, nodule number, nodule dry mass, N fixed and root starch concentrations in V.unguiculata decreased relative to both visible and UV-A radiation controls, whereas in G. max and P. vulgaris, these parameters were not altered. Root concentrations of flavonoids and anthocyanins in all species tested were also unchanged with below-ambient UV-B exposures. Taken together, growth and symbiotic function of these species remained unaltered with exposure to above-ambient UV-B, but differed in their response to below-ambient UV-B radiation.