Soybeans (Glycine max (L.) Merr. cvs. Essex and Williams) were grown in an unshaded greenhouse under two levels of biologically effective ultraviolet-B (UV-BBE) radiation (effective daily dose: 0 and 11.5 kJ m-2) for 34 days. Ultraviolet-B radiation reduced leaf area and total plant mass in Essex but these parameters were unaffected in Williams. Differences in both anatomical and biochemical characteristics were found between cultivars. Some of these differences were inherently distinct between cultivars while others were variable induced by UV treatment. Specific leaf weight, an estimate of leaf thickness, was unchanged in Essex but increased in Williams with UV-B irradiation. The relative increase in concentration of UV-absorbing compounds in leaf tissues after UV-B irradiation was greater in Williams. The composition of UV-absorbing compounds in leaf tissues differed between the two cultivars but was unaffected by UV-B radiation. Although total soluble proteins and total peroxidase activity were similar between cultivars, several electrophoretically distinct peroxidase activities were detected. (Copyright (c) 1988 Pergamon Press plc.)