The paper discusses separation of lysozyme from chicken egg white (CEW) by ultrafiltration using 50 kDa MWCO polysulfone membrane pre-treated with myoglobin. The transmission of lysozyme was about 26% higher with the pre-treated membrane than with the native membrane. The transmission of the other major CEW proteins, i.e., ovalbumin and conalbumin, were found to depend on the transmembrane pressure (TMP), transmission decreased with increase in TMP. Thus, using a combination of surface pre-treatment and TMP adjustment, conditions were obtained whereby lysozyme was totally transmitted while ovalbumin and other CEW proteins were almost totally rejected. At a TMP of 20 kPa, the percentage purity of lysozyme was about 18%, while at a TMP of 120 kPa, the purity was greater than 96%.