The biological function of amyloid beta protein precursor (ABPP) in nerve cells is examined by transfecting it into the B103 clonal nerve cell line which makes no ABPP and asking if a variety of biological activities are altered. Although ABPP is expressed by the transfected cells at high levels, there are no detectable differences between the ABPP negative clones and the clones expressing ABPP with respect to growth rate in high serum medium, dibutyryl-cyclic AMP-induced differentiation, or morphology on plastic culture dishes. There are, however, significant differences in a number of properties between the two groups of cell lines. Cells expressing ABPP adhere more rapidly and have an enhanced rate of neurite outgrowth on collagen substrata. They also grow more rapidly in low serum medium. Finally, the expression of ABPP weakly but significantly protects the nerve cells from amyloid beta protein and glutamate toxicity.