Several laboratory tests that are currently used for the diagnosis of lead poisoning in man were evaluated for the detection of lead poisoning in sheep given 3 or 10 mg Pb/kg body weight/day for 7 weeks. Urinary porphyrins and basophilic stippling of erythrocytes were not sensitive indicators of lead poisoning in sheep, while urinary lead and urinary delta-aminolevulinic acid concentrations were too variable to have diagnostic value. However, erythrocyte delta-aminolevulinic acid dehydratase was strongly inhibited by exposure to relatively low doses of lead, while blood lead concentrations gave an indication of the level of exposure to lead poisoning.