Users are known to experience difficulties in dealing with information retrieval search outputs, especially if those outputs are above a certain size. It has been argued by several researchers that search output clustering can help users in their interaction with IR systems in some retrieval situations, providing them with an overview of their results by exploiting the topicality information that resides in the output but has not been used at the retrieval stage. This overview might enable them to find relevant documents more easily by focusing on the most promising clusters, or to use the clusters as a starting-point for query refinement or expansion. In this paper, the results of experiments carried out to assess the viability of clustering as a search output presentation method are reported and discussed.