Measurements of similarity have typically been obtained through the use of rating, sorting, and perceptual confusion tasks. In the present paper, a new method of measuring similarity is described, in which subjects rearrange items so that their proximity on a computer screen is proportional to their similarity. This method provides very efficient data collection. If a display has nobjects, then, after subjects have rearranged the objects (requiring slightly more than n movements), n(n-1)/2 pairwise similarityes can be recorded. As long as the constraints imposed by two-diminsional space are not too different from those intrinsic to psychological similarity, the technique apears to offer an efficient, user-friendly, and intuitive process for measuring psychological similarity.