Pulmonary hypertension is a life threatening incurable disorder. The advances in physiology, genetics, and molecular biology have greatly improved our understanding of the cellular and molecular mechanisms underlying the disorder. In this review, the recent progresses in the understanding of molecular mechanism are presented. Many studies show that pulmonary hypertension is caused due to mitochondrial dysfunction, endothelin-1, prostacyclin and serotonin. These findings and their exploitation will hold promise to find novel treatment options for patients.