An experiment was conducted to investigate the relationship between blood hormone levels and light cycle on performance of Korean native chicken. One hundred and two Korean native chickens were grouped into three treatments of natural light cycle (Control), 13L:11D (T2), and 16L:8D (T3). The egg production, egg weight, feed intake, serum melatonin and estrogen level were periodically measured from 22 to 34 weeks, respectively. The laying rates of T2 and T3 were significantly higher than that of the Control (P<o.05), except for the last period of the trial. There was no significant difference in laying rate between T2 and T3. The egg weight of T2 was significantly heavier than those of the Control and T3 for the first four wk, however, the egg weight of the Control was significantly heavier than the other treatments for the rest of periods (P<o.05). At 30 wk of age, the serum melatonin content of T3 was significantly higher than that of the Control, but there were no significant differences among treatments for the rest of experimental periods. It appears that the melatonin has a role in egg production of Korean native chicken. The blood estrogen level of T2 was also significantly high compared to those of the other groups at 26 and 30 wk of age(P<0.05), but was not different from the Control at 34 wk of age. The light stimulation may affect both blood hormone levels after the onset of laying in Korean native hens.