An extreme sensitivity of pen-reared black ducks (BDs) to lead shot was observed incidental to development of an enzyme assay (Pain & Rattner, 1988). Intubation of pen-reared BDs with one no. 4 lead shot resulted in 60% mortality in 6 days. It was concluded that BDs were more sensitive to lead shot than expected, or that lead toxicity may be exacerbated by stressful conditions (elevated temperature, confinement in small pens). We reexamined lead shot toxicity in BDs and mallards (MLs). In winter 1986 (Ta=1.7-14.6? C), pen-reared and wild BDs, and game-farm and wild MLs were sham-dosed or given one no. 4 shot. After 14 days, dosed birds were redosed with two or four additional shot. Since the original observation of enhanced. shot toxicity to BDs occurred during summer, the study was also repeated in summer 1987 (Ta=I7:6-30.9?C), with pen-reared BDs and game-farm MLs. Mortality, overt intoxication, weight change, aminolevulinic acid dehydratase activity, and protoporphyrin concentration were used to compare sensitivity among groups. Sensitivity to lead shot was similar between BDs and MLs. However, the wild ducks appeared more vulnerable than their domesticated counterparts, and signs of intoxication were more pronounced in winter than in summer.