This study proposes a topic distillation algorithm that ranks the relevant sites selected from retrieved web pages, and evaluates the performance of the algorithm. The algorithm calculates the topic score of a site using its hierarchical structure. The TREC .GOV test collection and a set of TREC-2004 queries for topic distillation task are used for the experiment. The experimental results showed the algorithm returned at least 2 relevant sites in top ten retrieval results. We peformed an in-depth analysis of the relevant sites list provided by TREC-2004 to find out that the definition of topic distillation was not strictly applied in selecting relevant sites. When we re-evaluated the retrieved sites/sub-sites using the revised list of relevant sites, the performance of the proposed algorithm was improved significantly.