Lipovitellin (Lv) is the major proteolytic product of vitellogenin (Vtg) in the ovary and has been widely usedin studies of endocrine disruption. In this paper, a high molecular weight protein was purified from the ovary extracts ofNile tilapia () using gel filtration followed by ion-exchange chromatography. Results of nativepolyacrylamide gel electrophoresis (PAGE), lipid staining with Sudan black B, carbohydratestaining with Schiff reagent,and phosphorus staining with methyl green identified the purified protein as a phosphoglycoprotein. Using westernblotting, the protein was cross-reacted with the anti-goldfish Lv antisera. Native PAGE determined the molecularweight of the protein to be approximately 560 kD, and a single monomer of ~112 kD was detected by the sodium dodecylsulfate (SDS)-PAGE. Based on this characterization, immunogenicity, and molecular weight, this protein wasidentified as the Lv of the Nile tilapia. No degradation was observed under conditions of multigelation or incubation at37