The susceptibility of opportunist pathogens associated with chronic granulomatous disease (CGD) to the non-oxidative killing mechanisms of neutrophils has been assessed by incubation in human neutrophil primary granule lysate. The dose and pH-dependency of killing of Aspergillus fumigatus, Candida albicans, Escherichia coli, Nocardia asteroides, Serratia marcescens and Staphylococcus aureus differed markedly and may partly explain their virulence in CGD, in which oxygen-dependent killing mechanisms are defective. At the acid pH in CGD neutrophil phagosomes S. aureus, Ser. marcescens, N. asteroides and A. fumigatus spores were highly resistant but C. albicans a less frequent pathogen in patients with CGD, was much more susceptible.