Many reports describe the efficient derivation and expansion of neural progenitors (NP) from human embryonic stem cells (hESC). However, little is known about the signaling factors found within the neurosphere microenvironment that regulate NP maintenance and differentiation. We show that Wnt ligand and receptor transcripts are endogenously upregulated within neurospheres derived from noggin-primed hESC. In addition, neurosphere formation and size were significantly greater in the presence of exogenous Wnt3a compared to control conditions. Inhibition of endogenous Wnt signaling resulted in a significant reduction in the efficiency of neurosphere formation and overall size, due to effects on both NP proliferation and apoptosis. These findings demonstrate a requirement of Wnt signaling for maintenance, proliferation, and survival of NP when cultured in neurosphere conditions. © 2007 Elsevier Inc. All rights reserved.