The sizes of complete transcriptome come from clustered EST data. As the number of genes is quite different from the number of clustered EST, it is a problem how to use the data from EST databases. There are a few databases having EST fragments and mRNA assembled and clustered to reduce the redundancy for gene discovery, but different databases give different results. For example, the number of human UniGene clusters is about 120,000, while the number of unique sequences of human EST clusters in The Gene Index project (TGI) of Harvard University is 1,080,000 [13, 14] . The difference between the two databases is supposed to be that TGI separated alternative splicing sequences and tried to produce tentative consensus, while UniGene put all the overlapping sequences together in one cluster. However only knowing this does not help match the data from the two databases. We still did not know the actual size of human complete transcriptome.