Although there are a number of tools for annotating dialogue, little work has been done in visualizing differences among annotations. Visualization of differences in annotation should help in doing consensus annotation, refining an annotation scheme and training novice annotators. In this paper, we present a graphical Annotation Comparison Tool (ACT), which displays multiple annotations side by side and highlights the differences. The differences our tool currently captures are utterance segmentation, utterance order, speech repairs and utterance categories.