The similarity of structure and biological properties of hen’s cystatin and human cystatin c gives the possibility for application of egg cystatin in therapy and prevention of many illness. In the studies basic processes for isolation and purification of cystatin from hen’s egg using membrane filtration and affinity chromatography have been worked out. As the effect of diafiltration 40-65% active inhibitor was recovered from egg white or egg white solutions after lysosyme removal. It was found that quantity of active cystatin is not lowered if lysozyme was removed from egg white. Purification of cystatin with affinity chromatography led to 50% recovery of inhibitor from preparations obtained after spray drying of protein solutions. The amount of purified inhibitor was 3-4% lowered for preparations made from egg white after lysozyme removal.