Summary1In eight patients with petit mal EEGs (approximately thirty) were taken. During the seizure patterns various external stimuli were applied. In these cases clinical and electroencc‐phalographic changes were observed simultaneously and relationships between the two were studied.2In petit mal attacks there are various degrees of alteration of consciousness grading from almost no loss of consciousness to complete lapse of consciousness. Between subclinical and clinical seizures there is a transition, and it is difficult to determine a definite border line between the two.3liven in a single petit mal seizure the degree of disturbance of consciousness is not constant but is altered in various ways spontaneously or following various stimuli. This can be confirmed by applying various stimuli during die seizure.4There are often no changes in the seizure waves in spite of changes of consciousness during a petit mal seizure. Even though various responses are elicited by stimuli the petit mal waves sometimes continue unchanged. Therefore even though petit mal waves usually do show the presence of disturbance of consciousness, they do not always indicate the degree of alteration of consciousness during the seizur