I2D (Interologous Interaction Database) is an on-line database of known and predicted mammalian and eukaryotic protein-protein interactions. It has been built by mapping high-throughput (HTP) data between species. Thus, until experimentally verified, these interactions should be considered "predictions". It remains one of the most comprehensive sources of known and predicted eukaryotic PPI. I2D includes data for S. cerevisiae, C. elegans, D. melonogaster, R. norvegicus, M. musculus, and H. sapiens.