The purpose of this investigation was to produce a title list of current journals supplying upwards of 75 percent of demand at the Columbia and Yale Medical Libraries. Columbia received nearly 2,000 journals and Yale over 1,500; findings are based upon an analysis of canceled charge slips for issues published from 1959 through June 1962. This combined study of recorded usage for six months in the Columbia Medical Library (12.9 percent of circulation during January through June 1962) and for one year in the Yale Medical Library (12.5 percent of 1961/62 circulation) revealed that a core of 262 journals supplied 80 percent of use of titles published in the 1959 to mid-1962 period. However, it is probable that current issues of all titles received were used at least once within the libraries. Titles of sixty-seven journals which supplied slightly more than 50 percent of use are listed.