Exposure of adult humans to manganese (Mn) has long been known to cause neurotoxicity. Recent evidence also suggests that exposure of children to Mn is associated with developmental neurotoxicity. Astrocytes are critical for the proper functioning of the nervous system, and they play active roles in neurogenesis, synaptogenesis and synaptic neurotransmission. In this report, to help elucidate the molecular events underlying Mn neurotoxicity, we systematically identified the molecular targets of Mn in primary human astrocytes by using microarray gene expression profiling and computational data analysis algorithms. We found that Mn altered the expression of diverse genes ranging from those encoding cytokines and transporters to signal transducers and transcriptional regulators. Particularly, 28 genes encoding proinflammatory chemokines, cytokines and related functions were up-regulated whereas 15 genes encoding functions involved in DNA replication and repair and cell cycle checkpoint control were down-regulated. These results are further supported by data from real-time RT-PCR, Western blotting and flow cytometric analyses. In addition, analysis of common regulators revealed that 16 targets known to be positively affected by the IFN-gamma signaling pathway were up-regulated by Mn, suggesting that the proinflammatory IFN-gamma signaling pathway was likely activated. These results raise the possibility that inflammatory activation of astrocytes and the increased expression of proinflammatory cytokines and chemokines and/or the activation of related signaling pathways might be an important mechanism leading to Mn neurotoxicity.