Malignant gliomas are frequent and the prognosis is poor. The cytokine interferon gamma (IFN-gamma) enhances several immune phenomena and may be used in immunotherapy of tumours. Therefore we investigated the influence of IFN-gamma on human cell lines T98G, U87MG, 86HG39 and 85HG66, measuring cell viability (MTT-test) and proliferation (3H-thymidine uptake). IFN-gamma markedly decreased viability and proliferation of all investigated cell lines. Expression of CD44 and adhesion to hyaluronic acid (HA) are involved in glioma invasion. Influence of IFN-gamma on these two features has also been investigated. IFN-gamma markedly decreased HA-adhesion in all three investigated cell lines, whereas CD44 expression remained uninfluenced. To summarise, IFN-gamma strongly decreased cell growth and HA-adhesion of malignant glioma cell lines in vitro. We suggest further investigations to characterise better the role of IFN-gamma as a treatment opportunity for malignant gliomas.