Abman, Kinsella, and co-workers caution against the widespread use of nitric oxide (NO) gas in the neonatal intensive care unit.1,2 However, like other leading advocates of NO therapy, they limit their remarks concerning toxicology to a discussion of the risks of acute lung injury and methemoglobinemia. It must be remembered that NO may have other important side effects as well. In particular, NO inhalation in concentrations of 30 ppm prolongs bleeding time in rabbits and humans,3 making it a uniquely dangerous agent for use in preterm infants at risk for intraventricular hemorrhage.