||PaxDb is a resource dedicated to integrating information on absolute protein abundance levels across different organisms. Publicly available experimental data are mapped onto a common namespace and, in the case of tandem mass spectrometry data, re-processed using a standardized spectral counting pipeline. Data sets are scored and ranked to assess consistency against externally provided protein-network information. PaxDb provides whole-organism data as well as tissue-resolved data, for numerous proteins. This collection references protein abundance information by species.