Numerous studies have implied that enhanced cell-substratum adhesion plays a role in neurite outgrowth by neuronal cells. Using an extracellular matrix (ECM) produced by cultured corneal endothelial cells, we have investigated attachment and de novo neurite outgrowth by the pheochromocytoma cell line, PC12. PC12 cells were found to attach more rapidly and efficiently to the ECM than to plastic or collagen-coated surfaces. An extensive but temporary (5- to 10-day) neurite outgrowth occurred in the absence of nerve growth factor (NGF) when cells were on the ECM. However, long term neurite survival and further elongation required NGF. Our findings are consistent with the hypothesis that protein(s) in the ECM has an important role in neurite outgrowth. Thus, NGF may not so much initiate neurite outgrowth as it stabilizes neurites. ECM and NGF also were found to modulate cellular protein synthesis by PC12 cells. On ECM, a decreased synthesis of many high molecular weight proteins (Mr greater than 85,000) was observed in comparison to that of cells on collagen-coated dishes. The presence of neurites (in the presence of absence of NGF) as associated with the induction of the synthesis of a cellular protein (Mr = 55,000 to 56,000 and pI of 5.6). NGF was found to increase markedly the synthesis of two secreted proteins, while it drastically reduced the synthesis of all others regardless of the substratum upon which the cells were maintained.