Abstract. A study was conducted to evaluate the influence of three lighting programs (23L: 1D), (18L: 6D), and (12L: 12D) on live weight changes of American Bronze turkeys by Profile analysis technique. The F-statistics and Wilk’s Lamba statistics for testing group-response interaction or similar profiles suggested that there was a significant interaction effect (p<0.01). The effects of the three lighting programs on live weight gain appeared to be different throughout the study except for the last 6 weeks. On the other hand, the results of the present study suggested that the effect of the three lighting programs on live weight gain followed a similar trend or three lighting programs had similar physiological effect on live weight gain from 10th week on wards.