Cell cycle blockers inhibit growth in dividing cells, but promote survival of differentiated cells, including neurons. Low micromolar dopamine profoundly inhibited cell growth in dopamine transporter transfected SK-N-MC neuroblastoma cells by cell cycle arrest at G(1). This effect was independent of oxy radical formation, antagonized by transporter block, abolished by FeCl(3) and mimicked by the iron chelator deferoxamine. We propose that dopamine inhibits cell growth by its ability to chelate intracellular iron. This novel biological action unrelated to neurotransmitter receptors, second messengers or oxidative stress, observed in human neuroblastoma cells of striatal origin, may be important for cell differentiation during neurodevelopment and survival of differentiated dopamine (nigral) neurons.