The data of UniGene can be found at website: http:// www.ncbi.nlm.nih.gov/sites/entrez?db=UniGene. On the homepage of UniGene, you can see the number of Uni-Gene clusters of diverse organisms. Click on the organism name and enter the page of statistic data, you can see "Final Number of Clusters" and "Histogram of cluster sizes". With the number of total sets subtracting the number of cluster sizes with only one sequence, you can obtain the number of UniGene clusters.