Recombinant interferon-gamma (rIFN-gamma) has been described to enhance phagocyte functions in vitro and in vivo in several patients with chronic granulomatous disease (CGD). To demonstrate the clinical usefulness of this treatment, 128 patients were treated in a randomized, double-blind multi-centre study with a placebo preparation or with rIFN-gamma. We analysed parameters of neutrophil oxidative and non-oxidative metabolism in 16 patients enrolled in this study. No enhanced superoxide-release was observed in patients treated with rIFN-gamma compared to placebo-treated patients. Phagocyte cytochrome b558 content also remained unchanged. Levels of four non-oxidative antimicrobial proteins (cathepsin G, azurocidine, p29b, lactoferrin) rose, fell, or remained unchanged, irrespective of treatment with rIFN-gamma or placebo.