Originally devised as a notation to capture scenarios during analysis and design, sequence diagrams can also aid understanding of existing software through visualization of execution call traces. Reverse engineered sequence diagrams are typically huge and designing tools to help users cope with the size and complexity of such traces is a major problem. While preprocessing may be necessary to reduce the complexity of a sequence diagram, interactive tool support is critical to help the user explore and understand the resulting diagram. This thesis examines tool features necessary to effectively support sequence diagram exploration by reverse engineers. Features were derived from a literature survey and empirically evaluated using an exploratory user study. The tool features were further evaluated by situating them within theories of cognitive support.