Intracardiac and transpulmonary levels of natriuretic peptides (NPs) and cyclic guanosine monophosphate (cGMP) provide insight into the pathophysiology of pulmonary hypertension (PH) secondary to left-heart failure but have not been evaluated in established or suspected pulmonary arterial hypertension (PAH). Demonstrating adequate reproducibility of these markers is an important precursor to further study. We hypothesized that the reproducibility of intracardiac and transpulmonary NPs and cGMP is similar to the reproducibility of these markers sampled from the peripheral venous circulation. In outpatients undergoing right-heart catheterization for PH, blood samples were obtained from a peripheral venous site, superior vena cava, inferior vena cava, coronary sinus, pulmonary artery, and pulmonary capillary wedge position. At each site, a repeat sample was collected approximately 60 seconds after the initial measurement. Reproducibility was assessed using the slope of the regression line between initial and follow-up levels. We enrolled 10 patients: Six had PAH, two had pulmonary venous hypertension, and two had normal pulmonary pressure. At all sites, the slopes of the regression lines for BNP were close to identity. BNP was generally more reproducible than NT-pro-BNP. For the NPs and cGMP, reproducibility at intracardiac and transpulmonary sites was similar to the peripheral venous site. Reproducibility of NPs was not influenced by PH severity, access site, or time between measurements. The two patients with the highest transpulmonary pressure gradients had high transpulmonary BNP uptake, but their transpulmonary cGMP gradients were negative. In patients evaluated for PH, reproducibility of NPs and cGMP at intracardiac and transpulmonary sites is high and is comparable to that of peripheral venous measurements.