This paper discussed the contruction of topics to be tracked and clusters to be detected in topic detection and tracking (TDT) tasks. Single pas clustering was used to cluster the news articles. As a result,the TDT tasks contained a combination of a good and poor clustering performance based on the F1-measure.Therefore,the selection of clusters and topics from the clustering experiment is important in the tracking and the detection tasks.It has contributed towards the user experimental design. Keywords: Topic detection and tracking; single pass clustering; user tasks.