This experiment examined the effect that photoperiod has on the heterophil to lymphocyte ratio and the tonic immobility duration of laying hens. In the first experiment the effect of lighting programs (23L:1D, 14L:10D, 18.5L:5.5D) on the heterophil to lymphocyte ratio of 36 week old laying hens were examined. Three different breeds were used (Castellana, Prat and Vasca). The heterophil to lymphocyte ratio was not affect by the lighting regmine in all three genetic lines. The second experiment compared the tonic immobility duration of hens (Castellana x Prat crossbreed) that were exposed to either a 23L:1D or 14L:10D. Hens that were exposed to the 23L:1D photoperiod exhibited a longer tonic immobility response than those exposed to the 14L:10D photoperiod. The results show that the hens did have an increased fear response but not a stress response (based upon the heterophil to lymphocyte ratio) to the 23L:1D photoperiod. Thus, exposing hens almost continuously to light can negatively affect the welfare of laying hens.