While it is generally accepted that foveal visual acuity in the adult has reached an optimal value, claims for improvement of peripheral acuity with training in the adult persist in the literature. Practice effects in peripheral hyperacuity have been amply documented. A carefully controlled test is here reported to examine the influence of training on the resolution thresholds for two lines and on Landolt C acuity measurements in the retinal periphery in eight normal adults. It involved 11-30 daily sessions of 300 responses with feedback. In some observers the first day's results were somewhat poorer, but otherwise the threshold curves were essential flat. Yet in the same location vernier acuity could be improved by 50% in six training sessions. Sustained and lasting neural modifications in peripheral vision can take place in stereoscopic, orientation, vernier, bisection and time discriminations, but not in resolution and Landolt C acuities.