Neuron-glia interaction is considered to be important for the establishment and maintenance of neuronal shape and polarity during development. Glial cells release a number of trophic factors, many of which have not been fully characterized. In the present study, the trophic influences of conditioned media (CMs) of four glioma cell lines (T98G, Hs683, AC, C6) were tested on cultured hippocampal neurons dissociated from fetal rat brain. The survival of hippocampal neurons was enhanced by C6-CM, but inhibited by T98G-CM. The elongation of neurites was remarkably potentiated by C6-CM and T98G-CM. The other two CMs had little effect on neuronal survival and neurite elongation. These results suggest that different glioma cell lines produce and release different kinds and/or amounts of neurotrophic factors. Our experimental method may provide a suitable assay system for the identification of unknown trophic factors.