Epileptic spasms are the most frequent type of epileptic seizures in infants. They can also occur beyond the period of infancy, within the context of other epileptic encephalopathies or as an expression of a focal or generalised epilepsy. The clinical semiology of epileptic spasms varies greatly. They sometimes consist of very subtle clinical manifestations, which occur in series, without the typical axorhizomelic contraction, or in association with focal seizures. The critical EEG correlate is also very variable and basically consists of the combination of a hypervoltage slow wave, a bout of rapid low-amplitude activity or a diffuse attenuation of the trace. The electromyographic recording of both deltoids during the EEG-video study helps to detect clinically subtle spasms and to define certain features of them that are clinically hard to determine. The classic interictal EEG pattern of hypsarrhythmia, or one of its variants, is not always present. Epileptic spasms can sometimes be mistaken for another type of paroxysmal episodes that can be epileptic or non-epileptic, and the EEG-video study may play a key role for the differential diagnosis. Taken together, the findings from the EEG-video study allow an adequate diagnosis and classification of the different epileptic seizures and syndromes, which can optimise both the therapeutic management and aetiological investigation.