Pulmonary arterial hypertension (PAH) is a sinister condition that is often diagnosed late and is associated with a progressive clinical deterioration and premature death. However, over the past 10 years the field has seen a dramatic increase in the number of effective therapies underpinned by advances in our understanding of the pathobiology of this illness. Identification of dysfunctional signaling pathways in the pulmonary circulation provided novel therapeutic targets with the goal of reducing pulmonary vascular resistance and prevention of death from right ventricular failure. Treatment algorithms have now become more complex, with therapeutic options defined by pulmonary artery vasoreactivity, functional class, and response to treatment. Combination therapies are increasingly considered as clinical trials demonstrating the efficacy of this approach are emerging. Monitoring and measuring the response to treatment in clinical trials and clinical practice are evolving from the historical dependence on functional class and 6-minute walk test to include estimates of the delay in the time to clinical worsening and the response of emerging biomarkers.