Pulmonary hypertension is a common but complex clinical problem. When suspected in an appropriate clinical setting or detected incidetally, an array of investigative tools are employed with an intent to confirm the diagnosis, define aetiology, evaluate the functional and haemodynamic impairment, define treatment options, monitor the therapy, and establish long-term prognosis. However, no single tool provides comprehensive information that encompasses the aforementioned aims. Therefore, judicious use of these tools is of paramount importance, in order to maximise outcome and cost-effectiveness, while minimising risks and redundancies. Furthermore, a number of promising tools and techniques are emerging rapidly in the arena of pulmonary hypertension. These tools augment our understanding of pathophysiology and natural history of pulmonary hypertension. There is, therefore, increasing need for validating these emerging paradigms in multicentre trials. In this review, we focus on the tools commonly used to evaluate pulmonary arterial hyertension and also define some of the new approaches to pulmonary arterial hypertension.