We report the expression of different interleukins (IL) in four human glioblastoma and neuroblastoma cell lines. The glioblastoma cell line LI, expresses IL-1 beta and IL-6 mRNA, though not IL-2 and IL-4. The expression of the former gene is modulated by retinoic acid. Two cell clones [BE(2)-C and BE(2)-M17] as well as the neuroblastoma cell line SK-N-BE(2), from which both clones were derived, express IL-6 mRNA, but not IL-1 beta, IL-2 or IL-4. Both IL-1 beta and IL-6 cytokines are known to increase hypothalamic CRH mRNA, a gene reported to be expressed in all these cell lines. The production of both cytokines and neuropeptides indicates a complex dialogue between tumour cells and anti-tumour immunity.