While it may not be the cause, evidence from several studies that supports the fact that increased oxidative stress and reactive oxygen species (ROS) together with decreased antioxidant activity can contribute to enhanced pulmonary vasoconstriction, vascular remodeling, and right heart dysfunction in pulmonary hypertension. Despite this evidence however, it is still unknown whether or not an oxidant/antioxidant imbalance contributes directly to the development of severe PAH. Answering this question is the aim of the recent paper reviewed in today’s post by Jernigan et al., “Contribution of reactive oxygen species to the pathogenesis of pulmonary arterial hypertension”. ROS in PH Many