Vasoactive intestinal peptide (VIP) is a neuromodulator, growth regulator and secretagogue for neuronal survival factors. Moreover, VIP has been suggested to be a mitogenic factor for embryonic neurons in the sympathetic nervous system. We now show that VIP had mitogenic activity in a human neuroblastoma cell line (NMB), as measured by cell number and thymidine incorporation. This mitogenic activity was dose dependent and was decreased with culture maturation. Northern blot analysis revealed VIP mRNA transcripts in this cell line suggesting an autocrine role for VIP in neurogenesis.