Abstract 1. 1. Starch gel electrophoresis of Coturnix egg white reveals phenotypic variation of at least six different proteins. 2. 2. A “one gene-one band” hypothesis is postulated for lysozyme (two alleles), postalbumin (two alleles), X-protein (three alleles in one population, two in the other) and Y-protein (three alleles). 3. 3. This is the first report of egg white lysozyme (muramidase) variation which is classifiable in electrophoresis and which fits the fact that the enzyme has no quaternary structure. 4. 4. The X-protein in both populations consistently has a highly statistically significant deficiency of the presumed heterozygotes. 5. 5. Out of twenty-four different genetic loci Coturnix is polymorphic at thirteen (Edinburgh, unselected) and fourteen (Great Haye, selected for commercial characteristics) loci. The latter have more alleles at several loci. 6. 6. Genetic variation in Coturnix is discussed with reference to the natural history of the species, a recent demonstration that it is relatively resistant to some pesticides and the problem of “hybrid vigour”, both at the molecular and the population level.