Thirty one patients with P.M. epileptic crisis whose EEG showed centrencephalic disrythmia secondary to focal irritating activity where thoroughly observed. 19% of the cases showed centroencephalic disrythmia secondary to deeply situated focus and 8% to focus of cortical situation; in these cases the temporal projection was predominant. The clinical type of the crisis was analysed with emphasis on the fact that 8 patients did not show a "sheer" P.M. type crisis (absence): 4 showed mioclonic P.M. and 4 akynetic P.M. The high incidency of personal antecedents (33%) is emphasized.