ImageGrouper: Search, annotate and organize images by groups. In Content-based Image Retrieval (CBIR), trial-and-error query is essential for successful retrieval. Unfortunately, the traditional user interfaces are not suitable for trying different combinations of query examples. This is because first, these systems assume query examples are added incrementally. Second, the query specification and result display are done on the same workspace. Once the user removes an image from the query examples, the image may disappear from the user interface. In addition, it is difficult to combine the result of different queries. par In this paper, we propose a new interface for Content-based image retrieval named ImageGrouper. In our system, the users can interactively compare different combinations of query examples by dragging and grouping images on the workspace (Query-by-Group.) Because the query results are displayed on another pane, the user can quickly review the results. Combining different queries is also easy. Furthermore, the concept of “image groups” is also applied to annotating and organizing a large number of images.