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In 1997, Faraneh Vargha-Khadem and her colleagues published a far-reaching paper describing for the first time three patients suffering from a new syndrome: developmental amnesia. Twenty years later, we propose here to establish a picture of today's knowledge about this syndrome. This pure amnesic syndrome is usually due to neonatal hypoxic/ischemic episodes resulting in brain lesions and notably in bilateral hippocampal atrophy. While some studies have aimed at providing a refined description of the neuropsychological profile of these patients, others considered them as a way of testing the hypothesis about normal functioning. The methods used and the main findings will be covered in the present article. We will focus in particular on the studies that investigated episodic memory disorders, their consequences on new semantic acquisition, on projection in the past and the future, or on the sense of identity. Brain damage associated with developmental amnesia will also be described, based on single cases and group studies. Finally, we will discuss the diagnosis of developmental amnesia and emphasize that this syndrome may be much more frequent than initially thought.