During the 1980s a number of studies suggested there might be a role for interferon in the treatment of high grade gliomas. In the light of these reports a formal Phase II evaluation of human lymphoblastoid interferon (Wellferon) was undertaken in patients with high grade gliomas which had relapsed after conventional radiotherapy; 14 patients were treated and no objective clinical responses were seen. This indicates that the overall response rate to interferon therapy in this situation would be less than 20%. It is therefore concluded that interferon administration is unlikely to be of value in the management of relapsed high grade gliomas.