Development of a technique of preserving and staining egg yolks have permitted the number of days during which yolk is deposited in a follicle to be estimated. Whether the yolk structure of Adelie penguin eggs is similar to those of other penguins studied using this method and the time required for yolk formation was determined. Eggs were collected at Cape Bird at the end of the laying period ... from nests at colony margins. Laying dated were known for 6 out of the 9 eggs collected. Eggs were weighed and samples of albumen and yolk were removed for future biochemical studies and the yolk was fixed in 4% formalin at 65°C for 16 hours. Part of the yolk was stained with 6% potassium dichromate then washed with water. Slices 1-2mm thick were cut and photographed and counts were made of the pairs of light and dark rings.