Heritabilities for egg quality traits in Japanese quail are moderate to high, and there are strong genetic correlations between egg weight and its component parts. Egg quality is affected by selection on body weight, but these effects differ somewhat between experiments, maybe in relation to the origins of breeding lines. Selection on egg production could increase yolk content. Direct selection work on egg quality traits has shown that there was genetic variation for yolk-related characters. The ω6/ω3 PUFA ratio can be improved by selection.