PeptideAtlas began in 2003, and, over the years, data from 230 human LC-MS/MS experiments, comprising a total of about 55 million spectra, have been added. About 8% of those spectra could be assigned highly confident peptide identifications. Currently, the human PeptideAtlas contains about 4.5 million identified spectra corresponding to about 60,000 distinct identified peptides. These peptides map to 7553 highly non-redundant protein identifiers, covering about 1/3 of the protein-coding genes in the human genome.