We examined neuroprotective effects of growth inhibitory factor (GIF) on injured adult rat facial motoneurons. The right facial nerves of adult rats were avulsed and removed from the stylomastoid foramen, and an adenoviral vector encoding rat GIF and Myc epitope (AxCArGIFM) were injected into the facial canal. Animals treated with AxCArGIFM showed intense immunolabeling for GIF/Myc in injured facial motoneurons. Treatment with AxCArGIFM after avulsion significantly prevented the loss of injured facial motoneurons, improved choline acetyltransferase immunoreactivity and prevented the induction of nitric oxide synthase activity in these neurons. These results indicate that GIF may have therapeutic potential against degeneration of motoneurons in adult humans with motoneuron injury and motor neuron diseases.