Cationic fraction III from the lysosomes of normal human peripheral blood polymorphonuclear cells (PMNs) was found to contain superoxide generation enhancing protein (SGEP). Herein, we report on the influence of partially purified SGEP obtained from fraction III (subfractions III-5 and III-6), on various phagocytic functions of human PMNs. SGEP markedly enhanced intracellular bactericidal activity of human peripheral PMNs. The enhancement was time and dose dependent. It also reduced adhesiveness of the PMNs. SGEP did not influence chemotaxis, phagocytosis or phagocytic index. These findings are compatible with our original observation regarding superoxide generation enhancement properties of SGEP.