The Micropaleontological Reference Centers (MRCs) comprise large microfossil slide collections prepared from core samples obtained through the Deep Sea Drilling Project (DSDP) and Ocean Drilling Program (ODP). The MRCs have been maintained for three decades, largely as a volunteer effort by a global network of curators at more than a dozen institutions. They were originally intended to provide a permanent micropaleontological archive for the DSDP; however, as their geographic and stratigraphic coverage has increased they have become increasingly valuable for research and teaching. This article describes the MRCs and their current usage, identifies the need to maintain and improve the accuracy of the microfossil taxonomy upon which most DSDP and ODP geochronology is based, and cites the potential for the future use of the MRCs by the Integrated Ocean Drilling Program (IODP).