Most health professionals recognize that patients and other consumers of health care information are not familiar with medical terminology. When MEDLINE searching was restricted to the few who understood Medical Subject Headings (MeSH), medical terminology, and the intricacies of searching the database, there was little need to accommodate the uninitiated. Health professionals knew that over the years MEDLINE has adopted a number of mappings from entry terms to the MeSH headings. Many of these mappings are from the extensive entry vocabulary of MeSH, described on the home page as “over 300,000 terms.”* Because of this large entry vocabulary, a search for “heart attack” now maps to “myocardial infarction,” a term consumers are unlikely to use.