Sheep grazing metal-contaminated floodplain pastures across mid-Wales ingest high concentrations of lead (Pb) in vegetation and directly in the form of soil. Sheep whole blood analysis indicated that Pb concentrations can be significantly elevated for animals grazing contaminated sites: in winter/spring, a median blood concentration of 147 µg Pb l− 1 was found at the location with the highest soil enrichment of this metal compared to only 26 µg Pb l− 1 for the control flock. There was within-flock variability in blood–Pb concentration, and overlap between blood–Pb ranges in animals grazing control and contaminated sites, although use of the Kruskal–Wallis H test established a number of significant (P < 0.05) differences between the blood–Pb content of flocks grazing the various study locations. Despite total daily intakes of up to 723 mg Pb d− 1, only one individual sheep showed a blood–Pb content above the ‘normal safe’ concentration of 250 µg l− 1. Blood and wool analyses were found to have limited value for the diagnosis of environmental exposure to Pb, and further consideration of metal accumulation in offal, bone and muscle tissue is recommended.