Spontaneous and flash-altered multiunit activity MUA was recorded from the lobus paraolfactorius of young male quail reared in either long or short daily photoperiods. The birds were subjected to testosterone administration, castration, optic nerve section or retroparaolfactory disconnection and compared to intact controls. In all experimental and intact quail, iterative flashes led to decreased paraolfactory MUA. Spontaneous firing rates were found to be significantly higher during the light than during the dark part of the photoperiods, indicating some direct effect of environmental lighting on the paraolfactory neuronal populations. However, blinded as well as paraolfactory disconnected animals failed to exhibit any difference in firing rates according to the daily short and long photoperiods as seen in controls, suggesting that the light regime might also indirectly influence the paraolfactory activity.