Data from 210 articles and five unpublished studies were used for the meta-analysis. Articles were gathered using on-line databases (ScienceDirect, Wiley Online Library, Springer Link, PubMed and Google), using the keywords "virus-to-prokaryote ratio", "virus-to-bacterium ratio", "VPR", "VBR" and "viral abundance". Interesting reports were also found within the references of publications dealing with viral ecology. Publications were chosen according to the data they contained with a priority on articles containing VPR values (184 out of the 210 publications and four out of five unpublished studies) and viral abundance data. Articles lacking information on VPR and viral numbers were discarded (e.g. reports with only prokaryotic abundance, but lacking data on viral numbers, etc.), as the focus was on the ratio between viruses and prokaryotes. When data of interest were not available in the analysed reports, authors were contacted for more detail. When VPR values were not cited as such given within a publication, they were calculated according to the given viral and prokaryotic abundances provided therein. The file corresponding to our database was created by KJ Parikka. The doi was obtained by S Jacquet with INRA services.