Bovine growth hormone(bGH) is responsible for a variety of regulations on growth and metabolic processes of the animal. In order to increase the production of bGH in Escherichia coli, the coding sequence of a full-length bGH cDNA was cloned on a plasmid containing a high copy number mutant ColE1 replicon and various approaches to overcome the poor translational efficiency have been attempted. One approach was to modify the sequences in the first 9 codons of bGH mRNA ire order to alter the secondary structure of bGH mRNA. Another approach was to insert AT-rich block into the upstream region of SD consensus sequence enriching the spacer region with A and T nucleotides. Upon induction with isopropyl-β-D-thiogalactoside (IPTG), the recombinant bGH(rbGH) was overexpressed as a form of inclusion bodies, with its expression level reaching upto 25% of total E.coli proteins. The rbGH was isolated from inclusion bodies by solubilization in 10M urea and purified with DEAF-TOYOPEARL 650C and Sephadex G-100 column chromatography. The protein was renatured in 10mM of tris buffer, pH9.1 and purified the renatured bGH by reverse-phase HPLC. The purified bGH was characterized by N-terminal sequence analysis and radioreceptor assay.