Content and Impact Factors for the twenty biomedical journals with highest Impact Factors, 2010, listed in order of highest Content Factor.

The Impact Factor is calculated by dividing the number of current year citations to source items published in the given journal during the previous two years by the total number of source items; the Content Factor is the total number of citations in a given year to all of the papers the journal had published up to and including the year in question, reported in “kilo-cites” (ie thousands of citations).