Magnetic resonance imaging has become a widely used clinical tool for the assessment of neurologic symptoms, as well as being increasingly used in neuroscience research. White matter hyperintensities are common findings on brain imaging and their discovery leads to questions about best management, especially when findings are incidental or not considered relevant to the patient’s presentation. This review will discuss the varied causes of white matter hyperintensities, consider how best to distinguish between them radiologically, and when they might have potential clinical relevance.