Two glioma tumor lines and brain tumor specimens from 10 patients were analyzed to determine genic expression of insulin-like growth factor II. Messenger ribonucleic acid encoding insulin-like growth factor II was found to be expressed in significant amounts in two of two meningiomas but not in any of the gliomas. Immunofluorescence studies on these tumors and normal brain confirmed the presence of insulin-like growth factor II in both meningiomas, but not in any of the gliomas or in normal brain. Within the meningiomas, only a small number of cells highly expressed insulin-like growth factor II immunoreactive material, and this could be evidence for a paracrine mechanism in these tumors. These data suggest that the enhanced expression of insulin-like growth factor II may be a characteristic of meningiomas.