The cDNA coding for the mature beta-nerve growth factor (beta-NGF) has been cloned into a plasmid expression vector, pAS1, and expressed in Escherichia coli. The cDNA fragment in pAS1 is under the control of strong phage transcriptional and translational initiation elements that provide for regulated expression of cloned genes in E. coli. The protein, produced in bacteria at a level of about 0.0005-0.1% of cell protein, was purified by ammonium sulfate precipitation and ion exchange chromatography. The recombinant NGF was biologically active in the PC12 neurite outgrowth assay, and formed a band at Mr of about 11,000 to 12,000, when electrophoresed on sodium dodecyl sulfate-polyacrylamide gel and Western-blotted.