The creation of a thesaurus de novo is always a daunting task, especially in such a multidisciplinary field as health care informatics. This thesaurus had its roots in a historical collection at the University of Missouri-Columbia where the literature of the field has been collected since the 1970s. However, not only is informatics a multidisciplinary field, but it is also a rapidly evolving field, Thus, the need to be current balanced the historical perspective of the early collection. Generally, we have chosen to use the current term when the same concept has changed its nomenclature and, by and large, have concentrated on recent literature as the source for the data which resulted in the thesaurus.