A comparative index to the embryopathic effects of a number of metals which may appear as trace contaminants in avian food sources is given. Chicken eggs (White Plymouth Rock strain) were treated by yolk injection with sodium arsenite, sodium selenate and chloride salts of cadmium, lead, mercury, methyl mercury and zinc immediately prior to incubation. Eggs were positioned horizontally for 24 hr before injection, allowing the embryonic blastodisc to orient away from the point of needle entry. The test aliquot was deposited in a needle track extending through the diameter of each egg yolk, thus facilitating the uniform distribution of the toxicant. Percent survival was determined as hatchability in experimental populations/hatchability of controls. Survival rates at a concentration of 0.001 ppM were 64-66% for selenium, arsenic and cadmium at the same concentration, survival rates were 74-83 percent for lead, methyl mercury, inorganic mercury, and zinc. All metals produced appreciable percentages of teratogenic survivors when administered at or above their TL/sub 50/ concentrations. The greatest percentages of defective survivors were always at the highest test concentrations which permitted survival, ranging from 0.5 ppM for selenium and arsenic to 10.0 ppM for mercury and zinc. (MFB)