A study of epileptic drop attacks (EDA) by simultaneous video-polygraphic recordings was carried out in one epileptic patient with myoclonic astatic seizures (Doose syndrome). EDA was shown to correspond to a burst of generalized bilaterally synchronous spike and wave complexes (GBSSW) at 3 Hz. Absence seizures were also observed with a burst of GBSSW with similar characteristics. The amplitudes of the corresponding slow wave component of GBSSW among the three intensities of atonia, i.e. complete atonia, minor atonia and no discernible atonia (control), was compared. A high amplitude was demonstrated to correspond with more pronounced atonia and a lower amplitude with reduced or absent atonia. These findings suggest that EDA corresponding to GBSSW have a neurophysiological mechanism in common with absence seizures, and that if the GBSSW is intense, it may be sufficient to cause immediate loss of global muscle tone.