This paper presents a summary of the 1998 Topic Detection and Tracking (TDT) tasks and the results of the 1998 TDT evaluation. The purpose of TDT is to develop technologies for retrieval and automatic organization of Broadcast News and Newswire stories and to evaluate the performance of those technologies. The TDT project builds on and extends the technologies of Automatic Speech Recognition and Document Retrieval with three tasks: 1) Story Segmentation, 2) Topic Detection and 3) Topic Tracking. Each of the tasks simulates a hypothetical operational system that requires incoming data to be processed time synchronously. The 1998 TDT evaluation (TDT2) continues the work of the TDT pilot study conducted in 1997 (TDT1) and is the first open evaluation of TDT tasks.