Nitric oxide is a newly discovered gas that mediates communication bet
ween adjacent cells and signals inside cells. Defects in the nitric ox
ide signalling cascade have been found in patients with systemic hyper
tension, pulmonary hypertension, and coronary artery disease. High con
centrations of nitric oxide are cytotoxic. Over-production of nitric o
xide contributes to the pathogenesis of septic shock and uremic bleedi
ng. This review focuses on the cardiovascular and platelet actions of
nitric oxide, with emphasis on clinical studies of agents that modulat
e the nitric oxide signalling cascade.