Editing of the video image in computerized image analysis is readily accomplished with the appropriate apparatus, but slows the assay very significantly. In dealing with the cerebral cortex, however video editing is of considerable importance in that cells are very often contiguous to one another or are partially superimposed, and this gives an erroneous measurement unless those cells are artificially separated. Also important is elimination of vascular cells from consideration by the automated counting apparatus. A third available mode of editing allows the filling-in of the cytoplasm of cell bodies which are not fully stained with sufficient intensity to be wholly detected. This study, which utilizes 23 samples, demonstrates that, in a given area of a histologic section of cerebral cortex, the number of small cells is greater and the number of large neurons is smaller with editing than without. In that not all cases follow this general pattern, inadequate editing may lead to significant errors on individual specimens as well as to the calculated mean. Video editing is therefore an essential part of the morphometric study of cerebral cortex by means of automated image analysis.