Cicer milkvetch (Astragalus cicer L.) is a perennial, nonbloatinducing forage legume adapted to temperate environments. For unknown reasons, however, ruminants grazing cicer milkvetch in pure stands have become photosensitized, or sunburned, in some environments, Isoflavonoids are involved with diverse biological activities, including estrogenism, disease resistance, and, potentially, photosensitization. We conducted a series of studies from 1991 to 1993 to identify factors that influence the accumulation of isoflavonoids. In separate greenhouse studies, elicited leaflets from the parental clones of ‘Monarch’ and. ‘Windsor’ cicer milkvetch were analyzed for isoflavonoid accumulation. Growth chamber studies were conducted to investigate the clonal variability of leaflet isoflavonoid concentrations following different UV-C exposure times, incubation times, shoot positions, and growth × incubation temperature interactions. In both parental gene pools, clones differed significantly for the accumulation of mucronulatol, astraciceran, acicerone, and cajanin. The interactions of clone × UV-C exposure time, clone × incubation time, clone × shoot position, and clone × incubation temperature were significant for mucronulatol, astraciceran, maackiain, acicerone, and cajanin. Among all experiments, maximum mean concentration of mucronulatol, astraciceran, maackiain, acicerone, cajanin, biochanin A, and afrormosin was 2327, 152, 18, 63, 3, and 5 μg g−1 FW, respectively. Clone and environmental interactions with clones strongly influenced qualitative and quantitative accumulation of isoflavonoids in cicer milkvetch.