Since 1952, 20 datasets have been generated through 17 studies in an attempt to describe the sources and importance and/or use of information about pharmaceuticals by physicians. The authors review the findings of the studies and subject them to three sequentially relevant, but different, meta-analytic procedures. The results of these analyses indicate significant changes in the sources and importance of various commercial/noncommercial and personal/nonpersonal information as they relate to physicians' prescribing behavior. Those changes over time have specific implications for marketers of pharmaceuticals.