Studying the relationship between photoperiod and Melatonin hormone and its effects in regulating the immune response and affecting productivity is becoming increasingly important. The aim of the present study is to investigate the effects of different lighting programs in open side houses on Melatomin secretion and their effects on the productivity of broiler chickens. This study was conducted during the period of March to April 2000. All chicks were exposed to continuous light during the first three days of age, and then, exposed to specific three lighting groups with three replicates per group. The first group (ContinuoUs lighting) saved as a control and exposed to (23- hour light: 1 hour Dark). The second group (natural lighting) exposed to natural daylight approximately (11- hour light: 13 hour dark). The third group (Intermittent lighting) exposed to natural daylight and (1-hour light: 3 hour dark) during the night time. Birds raised on the continuous light consumed more feed, were heavier in weight during the first 2 vas, and had inferior feed conversion ratios than other groups. At marked age (6 wk) intermittent lighting group had significantly higher body weights and better feed conversion than both natural and continuous light groups. Birds raised on the natural light had the inferior body weight, feed consumption, while, feed conversion was similar to control. Intermittent and natural light was associated with . aduced total mortality and mortality from Sudden Death Syndrome (SDS). Electric used for lights with intermittent light group saved 82 % of that used with continuous light (control). The cost of broiler live weight with intermittent light group was less by 0.21 LE/ kg than continuous light (control).