Polynucleotide sequences which encode for human prepro insulin-like growth factors are provided. Such sequences are obtained from the human genome, typically by screening a cDNA library obtained from human liver cells. The polynucleotide sequences may be used for cloning and expression of insulin-like growth factors in suitable hosts, as well as for the production of DNA and RNA which may be used as hybridization probes.E. coli strains HB101(phigf1) and HB101(phigf2) were deposited at the ATCC on Jun. 8, 1984, and granted accession nos. 39729 and 39730, respectively.