Different radiologic indexes and measurements proposed in the evaluation of pulmonary artery hypertensión (PAH) were reviewed. The postero-anterior chest roentgenograms of 250 subjects were studied. In all cases the pulmonary artery pressure was known from cardiac catheterization. The diameter of the right pulmonary artery was larger than 1.7 mm. in 45% of cases with PAH. The pulmonary-lobar-transverse-thoracic index (PL/T) was abnormal (+38%) in 74% of cases with PAH, and normal in cases with increased pulmonary flow. The index of Ozawa, distance between the midline and the more prominent portion of the pulmonary arch, related to the transverse diameter of the left hemithorax overestimated the mean pulmonary pressure when normal and underestimated the same with PAH. A new index is described. The relation of the right pulmonary artery with the transverse diameter of the hemithorax on the same side (r/h index). It was abnormal in 24% of the cases with PAH and it was always normal in cases with increased pulmonary flow. The more sensitive and specific measurement seems to be the PL/T index.