A minimal EEG response can be used to study convulsive threshold in man. An EEG record is obtained, an intraven. injn. of metrazol is given, and the time at which the first change appears in the EEG is recorded. In rabbits, the mini- mal EEG always preceded the convulsion. When drugs changed the convulsive threshold, the EEG response changed in the same direction. Phenobarbital retarded the minimal EEG response and the convulsion. The response showed a lower threshold to dilantin. Diluting the metrazol raised the convulsive threshold and the threshold for the minimal EEG response. Phenobarbital and dilantin raised the threshold for the response in a few patients tested.