Waterloo, Ontario – Peptide identification is a central task in mass spectrometry based proteomics. Existing approaches include: (1) protein sequence database search with uninterpreted spectra, (2) de novo sequencing, (3) database search of de novo sequence tags, and (4) spectral library search. These approaches are usually performed separately according to the circumstances. In this abstract, we present the PEAKS-DB software that combines the first three approaches to significantly improve the sensitivity and reduce the FDR of peptide identification.