In situ expression of nerve growth factor (NGF) receptors in human dermal and plexiform neurofibroma, schwannoma and traumatic neuroma was examined by an immunohistochemical method using a monoclonal anti-human NGF receptor antibody. Immunoreactivity for the NGF receptor was observed on the principal cells of both neurofibroma and schwannoma. Immunostaining by the anti-S-100 beta protein antibody in adjacent sections suggested that the vast majority of NGF receptor-positive cells were also positive for S-100 beta protein. In traumatic neuroma, staining for the NGF receptor was more intense in the perineurium than in the endoneurial cells.