Warren and Higenbottam's commentary (Sept 7, p 629)1 is unhelpful. Inhaled nitric oxide (NO), like many other forms of therapy used in intensive therapy units (ITU), is indeed an unlicensed form of treatment, and it is correct to warn doctors that they are individually responsible for its use. Two large multicentre randomised controlled trials are underway in Europe and America on the use of NO in acute respiratory distress syndrome (ARDS), and will provide the answers we all seek. Hopefully, this will be followed by the issue of a licence for this indication. 85% of treatments used in ITU have no evidence to support their use.2 Work underway to prove efficacy of NO should be commended.