A cDNA encoding mature epidermal growth factor (EGF) was isolated and cloned into a pQE30 vector in which the His(6)-tagged EGF was expressed. pH-stat feeding of concentrated medium at the time of isopropyl beta-D-thiogalactoside induction and slug-feedings of the enriched medium during the induction resulted in a higher cell density and specific expression. Using a simple refolding protocol that consisted of 1 mM L-cysteine addition for a 1-h reduction followed by 5 mM L-cystine addition for oxidative refolding, we were able to convert nearly all EGF monomers into the oxidized form. Also, there folding aggregate was converted into the monomeric form. Approx. 50% overall yield was obtained from the dissolved inclusion bodies to a single peak under FPLC. We hope that the result of this study may provide information that is useful for the scale-up of the recombinant human EGF production process.