Experiments were conducted to evaluate the teratogenic potential of nickel chloride given to developing chick embryos. Nickel chloride was dissolved in saline and injected into chicken eggs at dosages ranging from 0.02 to 0.7 mg per egg. The injections were made into the air sacs of eggs at days 0, 1, 2, 3, and 4 of incubation. Control eggs were injected with an equivalent volume of saline (0.1 ml per egg); in all, 840 chicken eggs were used. All embryos were examined on day eight. The following malformations were observed: exencephaly, everted viscera, short and twisted neck, short and twisted limbs, microphthalmia, hemorrhage, and reduced body size. The dose-response relationship was observed in all of the groups tested. The toxicity and teratogenicity of nickel chloride was the highest in the embryos treated at day 2. The results of the present study indicate that nickel chloride is teratogenic.