The effects of epirubicin and retinoic acid (RA) as differentiation inducing agents on human neuroblastoma cell lines were investigated. We have compared the response of neuroblastoma cells to epirubicin alone, to RA alone and to combined treatment, with respect to neuritic processes outgrowth, acethylcholinesterase activity, growth inhibition and antigenic expression. The obtained data indicate that the combination of the two agents is able to produce a synergistic effect on differentiation and on growth inhibition.