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