The Ministry of Health, Labour and Welfare (Japan) has approved research into primary pulmonary hypertension (PPH) and pulmonary hypertension due to chronic thromboembolic and/or embolic disease (CTE-PH) to examine their epidemiology, pathophysiology, and develop new therapeutic strategies. The Respiratory Failure Research Group, with grant support from the Ministry of Health, Labour and Welfare, changed the diagnostic names of PPH and CTE-PH. The Specific Diseases Control Division in the Health Service Bureau of the Ministry of Health, Labour and Welfare supported our proposal. One of the major purposes of The Respiratory Failure Research Group has been to maintain and, if possible, promote patient quality of life and prognosis in cases of intractable respiratory diseases. The name PPH has been changed to "pulmonary arterial hypertension (PAH)", and the name CTE-PH has been changed to "chronic thromboembolic pulmonary hypertension (CTEPH)", in keeping with recent worldwide research progress in this field. PAH should be subdivided into different pathophysiologic conditions, such as idiopathic and hereditary PAH, PAH associated with connective tissue diseases, portal hypertension, congenital heart disease, persistent pulmonary hypertension in newborn babies, pulmonary veno-occlusive disease etc. Different therapeutic strategies may be adopted for different subgroups. Pulmonary hypertension due to left heart disease, lung disease and/or hypoxia and CTEPH should be excluded from PAH. Continuous monitoring of PAH and CTEPH is required in patients with these conditions, even if the degree of pulmonary hypertension is improved by therapeutic intervention, because these diseases are incurable.