This chapter discusses the rationale underpinning nailfold capillaroscopy (nailfold capillaries run parallel as opposed to perpendicular to the skin surface, allowing their structure to be visualised non-invasively) and then describes the different clinical indications for nailfold capillaroscopy. The main clinical indication for nailfold capillaroscopy is in the assessment of the patient presenting with Raynaud’s phenomenon (RP). How to separate primary from systemic sclerosis (SSc)-related RP will be described, with discussion of very early diagnosis of SSc (VEDOSS). Assessment of the patient presenting with other (‘non-RP’) features of a possible SSc-spectrum disorder will also be described. Prediction of disease trajectory in the patient with SSc will be mentioned very briefly (because this will be discussed in chapter “ Nailfold Capillaroscopy in Systemic Sclerosis (Including Associations) ”) and (again very briefly, because this will be discussed elsewhere) the role of nailfold capillaroscopy as a tool to monitor disease activity in patients with dermatomyositis. Monitoring disease activity in dermatomyositis is currently the second main clinical indication for nailfold capillaroscopy.