Velopharyngeal insufficiency (VPI) is due to an incomplete closure of the valve separating the oral and the nasal cavities and manifests as a nasalized voice, articulation problems, and sometimes swallowing disorders. The etiologies are anatomic, neurogenic or functional. The evaluation of VPI remains challenging and is the key to the management. This work provides an overview of current knowledge in velopharyngeal anatomy and physiology, VPI evaluation techniques and therapeutic modalities. A comprehensive review of literature is presented, with a focus on the controversial innervation of the velopharyngeal muscles and on the perceptual and instrumental evaluation of resonance disorders in VPI. Lastly, an attempt is made to identify the “grey” areas still existing in the field of VPI evaluation and treatment, and to define research perspectives.