The direct cortical response (DCR) is the potential recorded from a cortical locus in response to a surface stimulus applied 2 mm. or less away. It is presumed to arise in the superficial dendritic plexus. The human response has been examined previously by Purpura et al.1 and by us.2,3 In our work d.c. recording was used, permitting study of the late components which follow the 20 msec. primary negative potential* and of the negative potential shift which develops during repetitive stimulation. In our earlier study2 all recordings were made during general anesthesia of varying depth. Since then we have examined the details of DCR of rabbit, cat, and monkey with the view of determining the factors which affect the recording of each of the response components.4-6 In addition, changes in both early and late components due to anesthestic5 and convulsive agents7,8 have been observed,