Twenty-two eyes of 22 patients with initially normaly visual fields developed glaucomatous field defects. In 13 of these, the development of the definitive field defect was preceded by a localized minor disturbance in the area where the defect appeared subsequently. In a control group of 22 ocular hypertensives without field defects, six eyes had localized disturbances similar to those that preceded the field defects in the study group. This type of minor localized disturbance may represent an early glaucomatous visual change detectable before the appearance of definitive scotomas.