I'm not entirely sure what behavior you're looking for. Are you trying to implement expand/collapse user interaction, so that a set of gantt items can be collapsed into a single line? If so, this isn't built into the control and won't be easy to work around. You would have to implement FillSceneGraph event and manually show or hide gantt bars. If you want this to be a part of the control in the future, you can submit a feature request: http://devcenter.infragistics.com/Protected/RequestFeature.aspx