The objective of this study was to investigate the line-by-feed additive interaction on egg traits and yolk cholesterol level in laying hens. Hy-line W-98 (white shell line) and Hy-line Brown (brown shell line) were used as experimental stocks and three groups were assigned in each line. The age of hens used in this study were from 40- to 46-wk-old. Two different levels of chitosan were also used as additive in chicken diet. The first (CH

) and second (CH

) experimental groups were fed basal diet added 30mg and 60mg chitosan/kg feed, respectively. And the control group (CON) hens were fed with basal diet only. The eggs were collected and analyzed at the end of 40, 42, 44, and 46-wk-old. In the mean egg weight, the CH

in Hy-line Brown was significantly heavier (P<0.05) than CON, but the CH

in Hy-line W-98 was significantly lighter (P<0.05) than CON. Whereas, the mean egg weight did not significantly differ between CH

and CON in both line. The mean albumen percentage in Hy-line Brown did not show significant between experimental groups and control group. On the other hand, the mean albumen percentage of CH

in Hy-line W-98 was significantly lower (P < 0.05) than that of CON, but there was no significantly different between CH

and CON. In the mean yolk percentage, it showed a reverse trend as shown in the mean albumen percentage; there were significantly higher (P<0.05) in CH

than in CON fur the Hy-line W-98, and higher in CH

than in CON for the Hy-line Brown. However, the mean shell percentages did not significantly differ between experimental groups and control group in both lines. In the mean yolk cholesterol levels, the CH

and CH

in both lines were lower by 0.46 mg ∼2.80 mg per gram yolk than CON. Although the interaction effect of line-by-supplementing level of chitosan in hens diet on the pooled mean of yolk cholesterol level was no significant, it showed a highly significant interaction (P<0.01) at three of four experimental ages.