Human embryonic stem (hES) cells have the potential to form various cell types, including neural cells for the treatment of diseases such as Parkinson's, spinal cord injury, and glaucoma. Here, we have investigated the neuronal differentiation of hES cells on three-dimensional scaffolds fabricated from degradable poly(alpha-hydroxy esters) including poly(lactic-co-glycolic acid) and poly(L-lactic acid). When cultured in vitro, neural rosette-like structures developed throughout the scaffolds with differentiation dependent on factors in the medium (e.g., retinoic acid [RA], nerve growth factor [NGF], and neurotrophin 3 [NT-3]) and the differentiation stage of the cells. Specifically, enhanced numbers of neural structures and staining of nestin (a marker of neural precursors) and beta(III)-tubulin (indicative of neural differentiation) were observed with hES cell-seeded polymer scaffolds when cultured with both NGF and NT-3 when compared with control medium. In addition, vascular structures were found throughout the engineered tissues when cultured with the neurotrophins, but not in the presence of RA.