Nystagmus and other involuntary eye movements are a constant feature of insulin shock. During the course of shock these reactions undergo a constant and progressive series of changes which have a distinct relation to the depth of induced coma, as judged by other criteria. One first sees a nystagmus characterized by a slow and a fast component. This is followed by a spontaneous pendular nystagmus or by conjugate deviation. Later, all spontaneous eye movements cease but nystagmus can be still elicited by stimulation. Finally, a depth is reached where no eye reaction can be elicited and this is shortly followed by signs of respiratory depression. The course, in general, seems to be one of stimulation of eye movements initially, followed by gradual depression. While the exact sequence of events is somewhat variable, successive observations afford a useful and delicate check on the progress of therapeutic coma if they are used in conjunction with other findings. One can judge with particular accuracy whether a given coma is becoming deeper or lighter.