Some problems regarding the spawning of the Argentine anchovy Engraulis anchoita have been investigated. They are: (a) problems regarding the relationship between egg size and the size of the female, (b) variations in the dimensions of the eggs found in the plankton throughout the reproduction season and (c) the influence of the size of the eggs upon the development of the larvae. There is a positive (r = 0·4) correlation between egg diameter and the length of the female anchovy. There is great variation in egg size within the ovary of a single female. The most frequent differences (calculated from egg volume) lie between 1:1·5 and 1:1·6. The mean major diameter of the eggs for the females is 1·19–1·25 mm during the first year of life, 1·25–1·29 mm in the second year, and 1·29–1·32 mm in the third year. The differences in the size of the eggs found in the plankton within a single area, and during the same period of time, are considerable. They reach the ratio 1:2. The percentage values of the classes of egg sizes show little variation during the most intensive spawning, but there appears to be a tendency towards a decrease in egg size during the latter months of the reproductive period. This tendency seems to be independent of changes in the temperature. The size of the eggs has little influence upon the survival capacity of the larvae when there is a lack of food supply in the external environment. Larger eggs produce longer larvae with bulkier yolk sacs, but they consume more yolk. Under experimental conditions, where there is a lack of food, the larvae are able to live for up to eight days, and a very few, up to nine days. Disregarding any differences in fecundity, no significant difference appears to exist between spawning contributions of different age-groups of anchovies.