Pulmonary hypertension has been classified into five major subgroups in order to better understand and apply knowledge from the areas of molecular biology, pathophysiology and clinical science. Accurate classification of the patient not only optimizes diagnostic approach but also confers the best benefit, as therapeutic approaches are applied accurately. Current diagnostic strategies begin with a detailed history and physical, which are directed to elucidate symptoms that may increase the degree of suspicion. Subsequent application of a logical approach to progress through the diagnostic algorithm , with understanding of the complexity of this process, allows for best possible outcomes. Proper diagnosis and classification will eventually increase the potential for appropriate research and progress toward of a possible cure for this fatal disease.