Abstract: A ciliary neurotrophic factor (CNTF), particularly sciatic nerve CNTF (SN-CNFT) is claimed. The SN-CNTF described herein is a single protein species and has a specific activity that increased to greater than 25,000-fold from crude extract. The purification is carried out by lowering the pH of the crude nerve extract preparation to form a precipitate which is removed and discarded; raising the pH to about 6.3 followed by ammonium sulfate fractionation; chromatofocusing a solution containing a second precipitate obtained from the 30% to 60% ammonium sulfate containing solution; subjecting the fractions obtained by chromatofocusing to sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis (PAGE); and performing reversed-phase high-performance liquid chromatography (HPLC) on the SDS-PAGE eluate.Amino acid data for this SN-CNTF is also provided. In addition, methods for using this data for providing SN-CNTF probes and for screening cDNA and genomic libraries are also provided.