The first four automated visual field examinations of 20 patients with clinically stable chronic open-angle glaucoma who had previously undergone manual perimetry were studied for the presence of a learning effect on mean sensitivity, number of disturbed test locations, total loss, and short-term fluctuation. A learning effect, if present, would manifest itself as an improvement in the visual field as patients become more experienced with the test. There was no apparent effect of patient experience on the mean sensitivity, total loss, or the number of disturbed test locations. There was a significant (P less than 0.0001) decrease in short-term fluctuation as measured by the root mean square between the first and second visual field examinations. These results indicate that a learning effect did not play an important role in the clinical interpretation of automated perimetry in patients with glaucoma who have previous experience with manual perimetry. In most cases, it was not necessary to obtain more than one "baseline" examination unless a patient demonstrated unusually high short-term fluctuation or had visual field defects inconsistent with the rest of the clinical examination.