The past decade has witnessed a veritableexplosionof interest in the simplemolecule nitric oxide (NO) as a vasodilator, neurotransmitter, and antimicrobial agent. NO and other reactive nitrogen intermediates exhibit cytostatic or cytocidal activity against a remarkable breadth of pathogenic microorganisms. Mammalian cells, including human cells, produce nitric oxide both constitutively and inducibly in response to inflammatory stimuli. This review will provide a brief overview of current knowledge regarding the antimicrobial activity of NO and the possible importance of this activity in infection, particularly with regard to intracellular pathogens.