Interrupting petit-mal status in infantile myoclonic seizures (n = 11), Lennox syndrom (n = 32), and in myoclonicastatic petit mal (n = 13) diazepame (Valium) and clonazepame (Rivotril) have been injected intraveneously in 56 patients during continuous EEG monitoring (38 patients with diazepame, 18 patients with clonazepame) (Table 1). A judgement according to the EEG findings and the apparent vigilance was performed thirty minutes after the injection was completed (Fig. 1 und 2; Table 3). Following results are presented: 1) There are no significant differences between clonazepame and diazepame with respect to therapeutic success (Table 3). 2. There are almost no differences concerning therapeutic success in the three forms of petit-mal status listed above (Table 3). 3) The initial success was 57%: 46% in infantile myoclonic seizures, 56% in Lennox syndrome, 70% in myoclonic-astatic petit-mal. The number of relapses for all forms was high: On the day following the injection only 18% of all patients did not show continued petit-mal-status: 18% in infantile myoclonic seizures, 15% in Lennox syndrome, 23% in myoclonicastatic petit mal (Table 3). 4) 13 patients were no longer in a status on the following day. 3 children were out of status spontaneously, independent from the intravenous application, 4 patients, one with infantile myoclonic seizures and 3 with Lennox syndrome, showed a focal EEG, 6 patients, 2 with infantile myoclonic seizures, 3 with Lennox syndrome, 4 with myoclonic-astatic petit mal, were further demonstrating generalised paroxysms (Fig. 1 und 2). 5) In infantile myoclonic seizures and in the Lennox syndrome almost always a focal EEG could be seen that accompanied the decrease of generalised paroxysms (hypsarrhythmia or 2/sec slow wave and spike). This finding has not been seen in the myoclonic-astatic petit mal, another sign that the latter is of primary generalised, "centrencephal" origin in contrast to the first two forms of convulsive disorders (Fig. 1, 2).