Objective: The effects of proline-rich polypeptide (PRP) isolated from neurosecretory granules of bovine neurohypophysis produced by nuclei supraopticus and paraventricularis on phagocytosis, bacterial intracellular killing and oxidative burst induction in normal human cells and inflammatory cells from patients with Behçet’s disease (BD), i.e. peripheral blood neutrophils and monocytes, were investigated. Methods: Intracellular killing of Staphylococcus aureus by neutrophils and monocytes of normal controls and BD patients, phagocytic activity as well as spontaneous and N-formyl-Met-Leu-Phe (fMLP)- or phorbol 12-myristate 13-acetate (PMA)-induced activation of their respiratory burst were determined by quantitative flow cytometry using highly specific fluorescence probes. Results: PRP does not affect human peripheral blood neutrophil and monocyte phagocytosis but dramatically enhances spontaneous or fMLP- and PMA-induced oxidative burst as well as the intracellular killing of S. aureus. PRP induced the upregulation of the spontaneous or fMLP- and PMA-induced oxidative burst in normal PMNs and monocytes; the number of inflammatory BD cells did neither increase further nor undergo spontaneous or PMA-stimulated oxidative burst. In BD patients, increased spontaneous production of reactive oxygen intermediates (ROIs) by neutrophils and monocytes is characterized by impaired intracellular protein-kinase-C (PKC)-dependent oxidative burst regulation as well as overregulation of chemotaxis/inflammation-mediated respiratory burst induction. PRP restores rather the impaired intracellular PKC-dependent regulation of ROI production in inflammatory diseased cells than the chemotaxis/induction of the inflammation-mediated respiratory burst. Conclusion: We demonstrated the regulatory role for PRP on oxidative burst in neutrophils and monocytes from normal controls and BD patients. Our results suggest that PRP differentially affects both chemotaxis- and PKC-dependent oxidative burst in normal and inflammatory cells from patients.