The effect of lesions on nerve growth factor receptor (NGFr) immunoreactivity (IR) in motoneurons within the mature feline trigeminal motor nucleus was investigated. Ten days following complete unilateral retrogasserian trigeminal rhizotomy including transection of the trigeminal motor root, motoneurons within the ipsilateral trigeminal motor nucleus showed NGFr-IR. In contrast, motoneurons within the contralateral trigeminal motor nucleus and within both trigeminal motor nuclei in unoperated control subjects did not show NGFr-IR. It is suggested that the appearance of NGFr-IR in motoneurons within the ipsilateral trigeminal motor nucleus after rhizotomy represents an attempts towards recovery and may be associated with the regrowth of its cut axons.