Immunohistochemical analysis of five paraffin wax-embedded neoplasms was performed to elucidate the characteristics of bovine nervous-tissue tumours. In case 1 (peripheral neuroblastoma), the neoplastic tissue was characterized by the formation of true and Homer-Wright rosettes and the existence of neuron-specific enolase. The neoplastic cells were possibly more immature than those of common neuroblastomas, because similar features are observed in human malignant neuroepitheliomas. The neoplastic cells in case 2 (ganglioneuroblastoma) ranged from large cells with abundant neurofilaments to immature small cells, rarely with neurofilaments or glial fibrillary acidic protein (GFAP). Such expression suggests the presence of pluripotential cells. The neoplastic tissue in case 3 (anaplastic ganglioglioma) was strikingly polymorphous, and had five elements; neuronal, astrocytic, oligodendrocytic, spindle cell and small oval cell. The neoplastic neurocytes and astrocytes were, respectively, characterized by neurofilament and GFAP positivity. The neoplastic oligodendrocytes made a honeycomb appearance, and the neoplastic spindle cells and small oval cells were considered to be less differentiated. The tumours of cases 2 and 3, which contained poorly differentiated cells and revealed both neuronal and glial differentiation, may be specific to calves. In case 4 (schwannoma), almost all the neoplastic cells were positive for S100 protein, while S100-negative fibroblasts were present in many areas of case 5 (neurofibroma). These two tumours were readily distinguished histologically and immunohistochemically.