Ten forms of human epidermal growth factor/urogastrone (hEGF/URO) were purified from human urine by using reverse-phase high performance liquid chromatography (RP-HPLC) following kaolin adsorption, gel filtration and ion-exchange chromatography. All of these forms competed with ¹²⁵I-mouse epidemal growth factor (mEGF) for binding to EGF receptors, crossreacted with anti-hEGF and had the apparent molecular weight of 6000 on sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. However, the molecular heterogeneity of hEGF/URO was revealed by electrophoretic and PR-HPLC analysis.