The role of the anterior commissure in discrimination of and habituation to olfactory stimuli was studied in pigeons by measuring changes in the heart rate. In order to exclude any trigeminal response, we presented odorous stimuli to groups of pigeons with one olfactory nerve cut and either the ipsilateral or the contralateral nostril plugged. When the nostril involved in the experiments was on the same side of the cut olfactory nerve, the pigeons did not show any response, whereas they displayed changes in heart rate when the nostril tested was on the opposite side. In habituation transfer experiments were a control group of pigeons and a group with the anterior commissure cut, both of them subjected to a monolateral habituation training to amylacetate. Later, when the odour was presented to the opposite nostril, both groups maintained the habituation.