This controlled, prospective, nonrandomized clinical investigation has as its chief strength the fact that it was done in humans with active disease and apparently on fairly modest therapeutic regimens. The aim was to present the results of oxidative-stress biomarkers in humans suffering from pulmonary artery hypertension (PAH). Inflammation and oxidative stress are essential in PAH with increased lipid peroxidation and reduced antioxidant defenses. Twenty-four adult patients of both sexes, with a mean age of 21 years, were subdivided into 2 groups: a control group of 12 healthy, nonsmoking volunteers and a PAH group (PAHG) of 12 volunteers with PAH receiving outpatient treatment. Oxidative stress was evaluated by plasma activity of reduced glutathione (GSH); lipid peroxidation was expressed by malondialdehyde (MDA) and lipid hydroperoxide (ferrous oxidation of xylenol orange [FOX] assay); vitamin E was measured by high-performance liquid chromatography and tumor necrosis factor-α (TNF-α) by enzyme-linked immunosorbent assay. Statistical analyses showed significant differences for (1) the TNF-α measure, with highest values in PAHG patients; (2) the plasma GSH, with lowest values in PAHG patients; (3) vitamin E, with the lowest concentrations in PAHG patients; (4) MDA measure, with highest values in PAHG patients; and (5) the lipid hydroperoxide FOX measure, with highest values in PAHG patients. In conclusion, inflammation and oxidative stress are present in patients with PAH, as confirmed by increased lipid peroxidation, reduced GSH, and low concentrations of vitamin E.