This paper describes the design and some preliminary result of a visual study that was conducted over the WWW. The subjects connected to our server over the Internet, and their own computers were controlled with Java software to produce the visual stimuli. By these means we were able to access a large population of subjects at very low cost, and we were able to conduct a large-scale study in a small amount of time. We developed tools and techniques that allowed some degree of calibration of the display and the viewing conditions, so the result obtained from the different subjects could be analyzed. We found that we could get good estimates of gamma values and pixel sizes of the subjects' displays. However, we also encountered some problems that may limit the types of experiments that can be conducted over the WWW with the present technology. We found that we could not consistently control the presentation time of the stimuli due to inconsistencies between implementations of Java on different platforms.