Mallard (Anas platyrhynchos) ducklings were fed nickel sulphate in their diet from day one to 90 days of age. Ducklings fed 1,200 ppm nickel began to tremor and show signs of paresis after 14 days of dosage (age) and 71% of this group died within 60 days of age. Birds fed 1,200 ppm nickel weighed significantly less (P less than 0.05) at 28 days of age than birds fed the other diets. Weights of ducklings fed untreated food or dietary dosages of 200 and 800 ppm nickel diets were not significantly different (P less than 0.05). The weight/length ratio of the humerus (an expression of bone density) from the 800 ppm diet females was significantly lower (P less than 0.05) than the control fed females at 30 and 60 days and for all ducklings fed 1,200 ppm at 30 days of age. The organ-weight/body-weight ratios for heart, liver, and gizzard did not differ from controls or between any dosage group. Liver nickel residues from ducklings that died during this study ranged between 1.0 to 22.7 ppm and kidney residues ranged between 2.7 and 74.4 ppm. Liver and kidney tissues from all ducklings that survived to 90 days of age contained less than 1.0 ppm nickel.