Human epidermal growth factor receptor (EGFr) gene amplification, rearrangements and expression were studied in tumours of the human nervous system. EGFr gene amplification was studied in 46 brain tumours. Gene expression was analysed by northern blot in 37 tumours and binding of its protein to EGF in 27 tumours. The EGFr gene was simultaneously amplified (with arrangements in 12.5% of gliomas) and overexpressed in 53% (9/17) of malignant gliomas, but never in meningiomas. In five high grade gliomas, amplification was always associated with a high level of receptors. However, since high amounts of EGF receptors found in one glioma were not the result of gene amplification, several systems of deregulation in EGFr production may exist and could be located at translational and/or post-translational levels.